Bobb, please keep an eye on the linked ISPN issue from the original bug to get an idea of what to document for this.
The note seems to be over complicated for me, I'd change it simply to:
The default timeout for MapReduceTask is 0. That is, the task will wait indefinitely for its completion by default.
This bug's contents/fixes are now available on https://access.redhat.com/documentation/en-US/Red_Hat_JBoss_Data_Grid/6.3/