The grimoire is acting weird; I believe it showed 40k maximum when I got it, this morning it showed 30000 as maximum, now when I looked at it, it showed 20k maximum and didn’t show how much had I gained from it earlier.
While I initially was excited to get this reward, luck has so big effect on how this works and I felt quite annoyed after having collected only some 6000 gold after completing 15 challenges; I’ve had a bit better luck since that but still not feeling very happy about it.