tableActivity enhancer: what do the asterisks mean? (***)

The *** in the alert details indicates there are possibly excessive index reads.

If we find an index activity record where the index reads are > 1.5 * the table’s record reads, we write the “***” at the end of the line.

This indicates possible unexpected application behavior.  You should investigate the code.  There may be an opportunity for a code or index correction.