Ah, OK, that makes a lot of difference. If it is important to you, then you could get the participants to go through a screen-scaling process, using an object of known size, like a credit card:
But if the detail is important, then yes, just say that the font was scaled so that the maximum height of any letter did not exceed 4% of the height of the screen. NB, most readers won’t know what “height = 0.08” means as the setting is PsychoPy-specific, so you need to spell out its meaning (and to be interpretable, halve it to 0.04, as explained in that units page).