Do you mean...
...In addition to counting hi-lo? Just counting 7's vs 9's would be a very poor system.
Assuming you mean in addition to hi-lo, if you change the tags you have one of the oldest systems, initially developed by Koko Ita and known as "Green Fountain", the system was most recently marketed by Ralph Stricker "The Silver Fox" and Edward Early. It is not a bad system, it can outperform hi-lo in pitch games, but underperforms in the standard 6-deck game. It is slightly better for the play of the hands but it is also slightly worse for betting.
The indices to the count are/were sold by the above individuals and it is considered bad form, if not actual copyright, to reproduce the strike numbers on a public forum.