Hi there. I'd love to try this mod out!
Unfortunately it doesn't seem to do anything. I place the combinator down and hook it up to a chest with jelly in it. The jelly is spoiling over time but the combinator doesn't give any apparent way to read the spoil amount. How does it work?

perhaps the orientation is wrong, try rotating.
if that doesn't work, removing and replacing.
if still no, then that is indeed a bug and I would like more information so I can fix it asap.

Okay I was asking how the mod works since I couldn't find any instructions on it.
Since you mentioned rotating, I tried that. I did not realize that the way this mod works is you place it directly adjacent to the container you want to measure and then rotate it so that the probe end of the combinator is sitting inside the chest being measured. I recommend putting instructions somewhere so people know how to use the mod. Works pretty well! Thanks for making this.

Unfortunately, mods that read non-standard things from containers have no good interface. Every such mod I've seen relies on examining the container it's pointing at or away from, depending on the mod's author. (Pointing towards being a probe, pointing away bringing data out.)