Ogg, I think I found a bug. According to the book, you reduce the encumbrance of armor by 3 when you equip it, so only armors of enc 4+ should impact your encumbrance when you put them on.
I added a Heavy Clothing and equipped it, and it showed my encumbrance use as going up by 1. I expected that to happen when I checked "carry" but I also expected it to go away once I checked "equip" but it didn't.
This was previously identified and per OggDude will be corrected in the next build.