ratio's explained
 

A gear box ratio is usually expressed as to input vs. output.
Example:
A 15 tooth input gear and a 30 tooth output gear would be expressed as a
2 to 1, meaning the input turns 2 turns, and the output turns 1 turn.
This is refered to as a reduction gearbox.
If refered to as a 1 to 2 ratio, it would be used as a step-up gear box, meaning the output turns faster than the input.