This is what MarketInfo(Symbol(),MODE_TICKVALUE)) stands for. It is only described as Tick value in the deposit currency.
https://docs.mql4.com/constants/environ ... oconstants
I don't know how this is calculated exactly, but you can try to see what value it holds. I think that if your deposit currency is USD, then all */USD will give you the value of 1. And the value is different when currencies are crossed. If I am not wrong, this is the value of 1 pip for the currency you are in, measured in the deposit currency. Or maybe you ask for somethin something else.
If you ask for how much profit/loss will happen if we have 0.1 lot trade and the price moves with 1 pip, then this is easy calculation when yu are in EURUSD with USD as deposit currency. But in other cases I think MODE_TICKVALUE should be used. But I can admit that I am really, really bad in mathematics and I have hard times thinking for such otherwise simple calculations. So I'm only giving ideas 🙂