The multiplication with module 5 is: In the first we calculate the multiplication of the two values (example 2*4), then the result (=8) is divided by 5 and, the module is the rest of the division (=3). Examples are in the below table.
((2*4) % 5) = 3 why 8%5 = 1 and the rest = 3

Multiplicattion %5 | 0 | 1 | 2 | 3 | 4 |
---|---|---|---|---|---|

0 | |||||

1 | |||||

2 | |||||

3 | |||||

4 |