I started a fresh save and noticed a few more upgrades with their actual effect not matching the tooltip.
Mining speed: says +30%, actually +50%.
Smelting speed: L1 says +100%, actually +50%.
L2 says +500%, actually +200%.
L3 says +20k%, actually +500%.
L4 says 80k%, actually 800%.
L5 says 4m%, actually 10000%.
Max energy looks somewhat weird too. It seems to have more actual effect than shown instead.