I noticed something weird when leveling my BTN.

I was like level 34 at the time.

I was gathering lv 36/37 items.

Gathered around 50 of them.

When I checked the challlenge log, it was still at 0. (It was tue/wed)

Gathered a couple of lv 31/32/33 items.

Challenge log registered a few items and it was not at 0 anymore.

So it seems it must be of the same "set" of items of your level... 31-35, not 36-40.

Really stupid implementation imho.