shift to the center of pixel?

I'm confused that since the boxes is not normalized yet,why add 0.5?
[https://github.com/facebookresearch/segment-anything/blob/6fdee8f2727f4506cfbbe553e23b895e27956588/segment_anything/modeling/prompt_encoder.py#LL95C18-L95C18](url)
So do the point prompt.
I'll be appreciated if you could help me.

Start in segment_anything/modeling/prompt_encoder.py at the linked line and inspect the box and point prompt coordinate transformations. Compare the 0.5 offset with the model's coordinate convention and related code, then confirm the intended behavior with the maintainer; the issue does not specify a concrete code change or test for completion.

Written by the indexing model from the issue text.