Don’t know what laser you use(which brand) but in GRBL(arduino) you can tell how many pulses is 1 cm. Calibrating is telling the number of steps per cm.
Looks like the Ortur LaserMaster 2 is GRBL based from what I could quickly find. Like @Har4har says, you can configure the number of steps per millimeter to be taken by the laser. Look at your configuration through LaserGRBL (https://lasergrbl.com/configuration/) and pay special attention to settings $100 and $101 (X and Y steps per mm respectively).
If they’re set to different values, but your laser uses the same drive ratio and microstepping settings for both axes, there’s your problem. If one of the axes is actually accurate, set the other axis to the correct axis’ value and you should be good. In both axes are off, set both to a convenient (round) testing value and cut a square to measure and calibrate.
Have you turned on the Rotary setting, by chance? That would affect the Y axis scaling. (Edit > Rotary settings, then make sure the Enable switch is off / red)