The rate from bones/skulls to ribs is off.

It trades 1:0.75.
It should trade 1.25:1, which is 1:0.8. ;) Not 1:0.75

If it's 1:0.75, like it is now, five skulls/bones result in 3.75 ribs.
(1 skull = 0.75, 2=1.5, 3=2.25, 4= 3.0, 5= 3.75)
But it should be - at least according to the picture/banner/link - 1.25:1.
Then five skulls/bones should result in 4 ribs.
(1.25 skulls =1, 2.5=2, 3.75= 3 and 5=4)

So yeah. I guess you guys get what I mean.