Okay, so picture it this way. There are <u><em>24 counters.</em></u>
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
There are <u><em>three rows</em></u> above in the example. In each row, there are<u> 8 counters.</u>
I you multiple 8 and 3, you will get 24 counters. Therefore, the answer is: Yes, Descartes is correct, because he is able to split 24 evenly in 3 rows without there being an extra counter left out or missing.