Debugging to Understand the process?

Hi Experts.

My company went back to work with the module 'RE'.

I'm working with functional FI working like RE.

Occurred a  Dump:  (Overflow during the arithmetical operation (type P) in program).Please see attached file.

- REAJPR Transaction.

-The error ocurred in productive envoirement.

-The functional didnt find in configuration the motive of DUMP.

-The error ocurred because a field size receiving incompatible variable .i find a sap note ,etc...

ld_indexchgperlast = abs( <ls_recindex>-indexchgpoilast ). 

-But the functional sayed that error ocurred because the wrong value in variables and he wants that i debug and understand how this

variables are fulfilled.

-I debugged and found

rd_indexchgpoilast = ld_dateindexbase - ld_lastadjmindexbase.

Now i need  to understand  how this variables ( ld_dateindexbase and  ld_lastadjmindexbase ) are fulfilled.

Somebody know a way to do it ?

With debug its very very hard and tiresome.

I accept suggestions.

thanks a lot.