Help with the Scale bar

I cant for the lifetime of me perceive how a scale bar is meant to work, for instance right here in my drawing I’ve a scale bar it’s scaled to be every centimeter is 1 meter on paper however I would like this classroom to remain this huge trigger if I scaled it down in order that the doorways are 1.5 meters (their correct size) the drawing can be too small on paper and the size bar can be enormous, I actually can't perceive how is that I can go away my drawing the identical measurement the doorways are roughly 2.5 cm on this scale (they need to be 1.5cm in 1:100 scale) and add a scale bar that’s truly correct

https://preview.redd.it/kp6jnwo1djzd1.png?width=1004&format=png&auto=webp&s=b06c18c6bc9c8eee28d0e0399b99d2bf149abc3f