Minecraft version & Mod Version:
The minecraft version is 1.12.2 and the mod version is 1.7.9

Single player or Server: Only works on singleplayer as far as I know.

Describe problem (what you were doing / what happened): After I put one of something into my storage system, it would say that 2 of that thing was in the system, even though there was actually only one of it. THIS DOES NOT DUPE THE ITEMS instead, it forces me to divide the amount by 2 in my head to know how much I actually have. Also, the pictures are from a creative world that I created after I noticed the issue in my survival world.

Yes its correct, if you connect the same inventory twice it will read the item twice. previous report #84 . i tried adding a check for it but it added lag . and as long as the builder is careful its not the worst, since as you said its visual only so does not dupe