I think it's this setting in the of Netsight Console options menu...
Number of Rows to keep in Event and Alarm table
Just click on help in the lower/right to get the explanation for it.
In short...
Clip to nnnn rowsThis value sets the number of rows that will remain in the table when the clip limit is exceeded.
Clip when above is exceeded by nnnn rowsThis value, added to the
Clip to nnnn rows setting determines when the table will be clipped (trimmed to the value of
Clip to nnnn rows).
-Ron