The ABB 2CSR255180R1165 DS201 B16 A30 is a residual-current circuit breaker with overcurrent protection (RCBO) rated at 16 A, 2-pole, with 30 mA trip sensitivity, part of the System Pro M Compact range.
The 16 A current rating covers lighting, small motor, and general-purpose branch circuits up to that load. Two-pole configuration switches both line and neutral, which is standard for single-phase RCBOs in most distribution boards.