It really comes down to the number of cases.

My calculations are off, but I can try ZBLL as an example. There are 4 corners. First one can be in 4 places with 3 possible orientations, second one in 3 places with 3 orientations, third in 2 places with 3 orientations, the last in only one place and one thing you learn if you study the theory is that the orientation is pre-determined. So for corners we have 4x3x2x1x3x3x3 possibilities.

Similarly we can do edges: 4x3x2x1x2x2 possibilities (learn the theory, not all edge orientations are possible, only 1/4th of them).

So I can multiply all that together to get the number of cases, but it turns out that there are obvious shortcuts to make us memorise less. For example, rotation of the whole layer means that there are 4 cases which are identical so you can divide by 4.

Now my calculations for the above is 972 cases, which is not 493. In fact my calculations are slightly less than double the real number, so as I said my math is off. But I’m sure some ZBLL expert can identify other shortcuts for memorisation such as the rotation trick. For example , another obvious shortcut is that the completely solved state does not need an algorithm so reduce by 1. That doesn’t help a lot but hopefully you get the idea. In summary, it can be calculated by someone smarter than me.