I studied a bit through books, and talked to electronics teacher in our university.
He confirmed that if the ESC ar in parallel the amperage should be summed up afterwards adding all servos, FC, etc. basically everything that draws energy. But he was not sure, because, he needed more info about how ESC worked and how the meter is working in this particular case, as he has not worked with multicopters. Because he didn't think that the ESC constantly draws 70 amps, and I believe ESC don't do that.
So because I'm building large multicopter 70A ESC with 8 of them, I need a pretty dam big meter about 600A
But I'm pretty sceptical about this(thats a VERY big meter required) so I will continue research and I will replay once I get this clear.