I think this is correct, it is doing what I want it to do :)
Instead of double random, if you have a random between 1-100, it means that each number has 1% of drop chance, so for multiple itens you could use like:
If random result is >=1 and < 5 = Drop item 1 (This means that you have 5% drop rate)
and a second condition
If random result is >=5 and < 8 = Drop item 2 (This means that you have 4% drop rate)
..
If random result is = 100.. Drop item 80 (This means that you have 1% drop rate)
Using just 1 random and multiple comparations