Often, the same error is seen while entering values in the webpage itself.

[Workspace]: p4 counter change
FATAL: For input string: ""
java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:470)
at java.lang.Integer.parseInt(Integer.java:499)
at com.tek42.perforce.parse.CounterBuilder.build(CounterBuilder.java:43)
at com.tek42.perforce.parse.Counters.getCounter(Counters.java:60)
at hudson.plugins.perforce.PerforceSCM.checkout(PerforceSCM.java:357)
at hudson.model.AbstractProject.checkout(AbstractProject.java:1024)
at hudson.model.AbstractBuild$AbstractRunner.checkout(AbstractBuild.java:479)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:411)
at hudson.model.Run.run(Run.java:1198)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:122)

It's an issue with input handling, I assume. No values can be configured for perforce through the webpage atleast.