Bad Support Gem Math...

The cooldown recovery rate for frostbomb is 6 seconds... the cooldown recovery 1 support says its 25% cooldown recovery. This would mean the cooldown should now be 4.5 seconds. Why does it say my cooldown is 4.8 seconds? This would mean its only 20% cooldown recovery rate instead of the stated 25% the support should give.

Is this labeled incorrectly, or is it just bad math? With all the other math involved in damage, armour, etc... its hard to believe this is just an 'overlooked' figure, as simple as it is in comparison.

Can we trust the rest of the math in this game is not skewed 5%, or more?

No, it's not bad math (by the game).

Rate is speed.
If you move 100% faster, how much time do you need? 100% less and therefore 0 time needed? NO!
You have to divide by the rate / speed. 100% basespeed + 25% increased speed = 125% total speed. 6 / 1,25 = 4,8. It works.

Is there a place where I can find more of these equations? I'd like to see more to better understand my choices in the game.

Thank you for the explanation.