Update size not matching estimate

Using Pop!_OS 22.04 LTS I have several apps installed as flatpaks. When I run ‘flatpak update’ it seems to update any apps needing updates, but the size of the updates themselves don’t match what looks like an estimate of the size.

Is this normal?
Are flatpaks like containers that have layers and only parts of the flatpak is updated?

An example:

  1. [x] org.freedesktop.Platform.GL.nvidfia-515-65-01 1.4 u flathub 364.2 MB / 365.1 MB

That appears to say there will be 365.1 MB downloaded but only 364.2 MB is ever downloaded. This difference is small but sometimes the downloaded size is only a small fraction of what I assume the total size or estimated size is.

It’s a known issue. See here: