Tween[-100..100%]

Tweening can be used orient the animation of a selected object at the current time to a previous or following keyframe value. Keyframes will be created at the current time whose values can be defined to lie between those of the neighboring keyframes using an interactive slider (which can optionally be displayed in the Viewport).

-90 %

-75 %

-50 %

0 %

+50 %

+75 %

+90 %

See the section described above, only that here you can define fixed percent values.