Hi,
2LIS_13_VDITM - data sources get data form the VBRK table, those are billing related tables (VBRK AND VBRP)
1. already have mapping from 2lis_13_vditm - to net values
2. have you fill the setup table multiple times for particular sales order?
pls check
if it is dev system pls delete the data form particular sales order and ECC side delete the setup tables and reload it again
check the results for object
Thanks,
Phani.