Why would they shim this? (photo)

[Marje]

I have a photo with shims in place. I do not understand what benefit the shims would provide. Any ideas why one would put them there and if I can remove them?

[Casita Greg]

Perhaps a real photo, rather than a plan layout drawing, would help better to see the condition you have described. The drawing really doesn't show very well what you're trying to depict.

[redbarron55]

The shims are probably to correct the drain level in the front bath, when so equipped.