The engines may accelerate slightly differently, resulting in an asymetricasymmetric thrust. Spooling up slowly at first (normally to about 60% N1N1) prevents this. After that, you can accelerate up to full togaTO/GA (or press the button) without any significant assymetryasymmetry.
Copy edited (<https://en.wiktionary.org/wiki/asymmetric#Adjective>, <https://en.wikipedia.org/wiki/Takeoff/go-around_switch> and <https://en.wiktionary.org/wiki/asymmetry#Noun>).