Hey,
how are the drop chances calculated?
if i count all % in my mine I get over 131% which would mean that there is always a drop.
Chances are not 100% drop so this is not split for each resource. If there is a (for example) 70% chance for Stone and 40% chance for Coal, the total is not 110%, but the chances are individual.

Your answer in not much clear to me. I guess you mean something as follows.
Let's keep your example: only two available drops, Stone with 70% chance and Coal with 40%. When I click the Mine button, I have the same chance of mining Stone or Coal. If I mine Stone I have 70% chance of finding it (and 30% of finding nothing); if I mine Coal I have 40% chance of finding it (and 60% of finding nothing).
Is my interpretation correct? If not, could you please explain the right one?
Another related question. Precisely, how are the chances affected by drop rate upgrades?