When we post retirement via AS91 or AS92, we could find system has default the field is positive or negative.
For example:
Enter revaluation amount 10000. Then enter, the amount will show as -10000.
System will do following check in SAPLALTD, include LALTDI0S:
CASE TABW_ANSHKZ_TMP.
WHEN 'H'.
......
IF GT_ANTVAL-AUFWV > 0.
GT_ANTVAL-AUFWV = 0 - GT_ANTVAL-AUFWV.
ENDIF.
......
Here we could find if we enter a positive revaluation amount, system will change it to negative.
For other transaction, we could also check the default amount is positive or negative here.