Hi Narayana,
just check docu in V_T706K view for column KEY - (The value of the formal parameter USERS in the routine FORM EXB706K in include RPREX010 of RPRFIN00 is used to read table T706K. )
Best practice for advances to post them to GL advances. Travel Management takes care about this payment in Cluster Segment ROT (Result table for postings)
You can check this via transaction PRTE (to read all important data about one trip, Cluster data TE and transparent table entries)
Posting will be done against employee vendor. After trip is done only the difference will be paid to the traveller. If the advance was higher than the reimbursement amount the vendor account will not be cleared and will wait until next reimbursement amount will come ... and so on....
Hope that helps,
Sigi