LP08.3 and Subtract versus Include

We are in the process of moving from 8.1.ESP5 to 9.0.0.6.  It looks like the functionality between what LP08.3 and the efffect of the settings for 'subtract' and 'include' have changed quite a bit.   Has anyone seen this behavior before? 

Specifically in production the subtract removes hours so as an employee takes vaction the hours are subtracted from their balance

In are dev 9.0.0.6 environment subtract actually adds the hours so as the employee takes vaction they get more and more time.

I think this is a bug we should definetly live with but the business seems to think that infinite amounts of vaction would be a bit too much.     ;)