Release the button when green LED starts flashing, to reset RouterOS configuration. To not load backup boot loader, you can start holding the button after power is already applied.
Дядька грозился шо: It allows to have 40Gbps NAT on commodity servers like 2*Xeon E5-2698 v3 @ 2.30GHz (2 x 16 Cores) with Intel X710/XL710/X540 10G adapters.