Viewport scaling

Hi, I have a problem with a viewport scaling. For some reason, I can't set up my custom vieport scale. My drawing is in meters, so i'm trying to get 1:500 actual scale. It means, I need to set up custom scale on viewport properties to 2. When i'm trying to do this, the model in viewport gets so big, as if it was in 1:2 scale or similar. Also, it does not set up standard scale to 'Custom', it keeps coming up '1:100'. I think, that's the reason why view doesn't coem up in right scale. Any ideas how to fix it?

When you adjust your scale, are you using the paperspace? If so you, you may want to adjust your paper size.

It was already done

it was old drawing and it was drawn to scale. I checked the measurements, they were not the same as dims said. once i scaled it to actual size, everything's ok:) thanks:) from now on I will always check everything, what I didn't do myself:)