The GA N1 value will be a reduced value (unknown) to give you a rate of climb 1500-2000fpm with the first push of the TOGA buttons. A second push will give you a full rated thrust Go around. This N1 value can be seen on the N1 gauge with a green carrot (>) when G/A is announced OR on the N1 limit page.
If you would like to find out the Go Around value before departure you could look in the Performance Inflight tables in the FCOM 1 manual.