Please tell me it is safe to connect these two wires even though there is a big discrepency in wire thickness.

I ordered three sets of these motor/ESC combos.
The motor is a Waypoint 2205-36 TURN, 1770KV, 28G brushless motor which states it can use an ESC from 10-20+ amps.
The ESC is a GWS speed controller 15 amp.