Sololocust

Hi all, I’m pretty new at 3d printing but I have managed to print a working box but wanted to put a symbol on it. So I printed the symbol is around 50 mm long and 2 mm in height. My first attempt was not good but I reduced d the speed to 50 and it came out like this. My question is the side that came out squashed is due to bed leveling or another Slicer setting? thank you very much in advance!!