Step increment is always X2

Hello,

On WEB, lately I just realized that the step, on using the mouse wheel, is always multiply per 2.
For example if the step = 1 the next number after using the mouse wheel will be +/- 2.
If the step = 3 the next number will be +/- 6.

Further more the only way to change the number is using the mouse wheel but if I recall good before can also be used the mouse.

Thanks for your help