You are mis-reading the specs - that HUB is powered by a 12v 5a (60w) power supply which has nothing to do with what each port can supply. That 12v is stepped down to 5v for each port but each port is still limited to 2.4a. Very few hubs support putting out 3a per port continuously.
How i underatand do i need in the Watt count? 12v*3A= 36 Watt 12*5A= 60 Watt but i also need to look how many ports mean with 5A and 4 ports i need a hub with 240watt? And the Watt can be splitted means if i have 120watt hub with 4 ports and i have 2 miner i can run both of them. How many Watt need a cooler fan?