As I understand plugin shows configuration in this way:
1. For projects with "Discard Old Builds" checkbox DISABLED plugin shows:
(Disabled) :: job1
2. For projects with "Discard Old Builds" checkbox ENABLED, but number of builds not specified plugin shows:
:: job2
3. For projects with "Discard Old Builds" checkbox ENABLED and number of builds specified plugin shows:
10 :: job3

If I'm trying to save this configuration:
---------------------
:: job2
10 :: job3
(Disabled) :: job1
---------------------

I'm getting:

--------------------------------------------------------------
Status Code: 500
Exception:
Stacktrace:

java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at configurationslicing.logrotator.LogRotationSlicer$LogRotationBuildsSliceSpec.setValues(LogRotationSlicer.java:145)
at configurationslicing.logrotator.LogRotationSlicer$LogRotationBuildsSliceSpec.setValues(LogRotationSlicer.java:99)
at configurationslicing.UnorderedStringSlicer.transform(UnorderedStringSlicer.java:33)
at configurationslicing.UnorderedStringSlicer.transform(UnorderedStringSlicer.java:8)
at configurationslicing.ConfigurationSlicing$SliceExecutor.transform(ConfigurationSlicing.java:84)
at configurationslicing.ConfigurationSlicing$SliceExecutor.doSliceconfigSubmit(ConfigurationSlicing.java:109)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:185)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:101)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:54)
at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:74)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:30)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:492)
at org.kohsuke.stapler.MetaClass$12.dispatch(MetaClass.java:318)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:492)
at org.kohsuke.stapler.MetaClass$12.dispatch(MetaClass.java:318)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:492)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:408)
at org.kohsuke.stapler.Stapler.service(Stapler.java:117)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:45)
at winstone.ServletConfiguration.execute(ServletConfiguration.java:249)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:335)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:378)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:333)
at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:244)
at winstone.RequestHandlerThread.run(RequestHandlerThread.java:150)
at java.lang.Thread.run(Unknown Source)

Generated by Winstone Servlet Engine v0.9.10 at Tue Jan 12 15:27:07 MSK 2010
--------------------------------------------------------------

This is probably due to " :: job2" field.

Also, if I'm trying to save this configuration:
---------------------
(Disabled) :: job2
10 :: job3
(Disabled) :: job1
---------------------
I'm getting result, that can be described in configuration as:
---------------------
:: job2, job1
10 :: job3
---------------------

But expected:
---------------------
10 :: job3
(Disabled) :: job2, job1
---------------------

Thanks!