When Fortnox corrects a voucher, the SIE file contains #BTRANS (added)
and #RTRANS (removed) lines alongside #TRANS (final state). The parser
was summing all three, causing corrected vouchers to appear unbalanced.
Only #TRANS represents the final voucher state — BTRANS/RTRANS are
correction audit trail.
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>