Rear derailleur adjustment screws My rear derailleur adjustment screws are in a vertical line there is no scew indicating inner and outer.  Without removing it I can't see which screw is touching at each side of the cassette. Does the upper screw relate to the big cog or the little one?
If you look straight down into the space between the parallelogram sideplates, you may see that the outer plate has a “feeler” that contacts one limit screw, and the inner plate a feeler that contacts the other.

If that doesn’t work, we can’t guess without knowing what kind of derailleur you have, and you can probably find service info on the manufacturer’s website.