i have at least 80 lbs+ on some of the shelves (attakus statues are super heavy!), not worried at all, those are thick wood shelves, they can be safely loaded up well above the 50 lbs stated. Also if it does hit the limit it wont crack instantly like glasses, you will see the fractures appear in time.
Only thing is make sure you use ALL 6 shelf brackets on the 2 sides to evenly distribute the weight, those things look kinda flimsy, basically just a screw as the weight bearer. I replaced them with 5mm metal pins from amazon below, little tougher to install as you have to twist it into place but much stronger.
https://www.amazon.com/gp/product/B002SV1U7G/ref=oh_details_o00_s00_i00