Hi,
While posting in New GL, if Leading ledger is involved, then entries are made in BSEG. If posting is ONLY for non-leading ledger , it will be posted only in BSEG_ADD table.
In the document ledger view, check the ledger group, if empty or it contains leading ledger - then posting line item data in BSEG. If the ledger group has only non-leading ledgers,then BSEG_ADD table.
Cheers,