Two decisions sit underneath every piece of motion you will make: how long something takes, and how far it travels between the frames of that duration. Timing is the duration; spacing is the distribution of distance inside it. Change nothing else and you change the character of a move.
Timing Is Duration, Measured in Frames
At 30 frames per second, a move over 10 frames reads as snappy and a move over 45 frames reads as calm or heavy. Count in frames rather than seconds while you work, because frames are the unit your software thinks in. A useful starting range for interface-style motion is 8 to 20 frames; title and brand motion often sits between 20 and 40.
Spacing Is Where the Weight Goes
If an object covers equal distance every frame, spacing is even and the motion reads mechanical. If the gaps start small, widen, then compress again, the object appears to gather speed and settle. Spacing is why two animations of identical duration feel different, and it is what you adjust when motion feels wrong.
Reading Motion as Distance Over Time
Step through your animation a frame at a time and note how far the object moved. Large jumps mean fast passages, tight clusters mean slow ones. Clustering at the start suggests a heavy object getting going; clustering at the end suggests arrival. Reading this pattern lets you diagnose motion instead of guessing at settings.
Action Step
Animate a ball crossing the frame in one second, three times over: even spacing, spacing clustered at the start, and spacing clustered at the end. Loop all three and write a sentence on how each one feels.
This lesson is educational and reflects general practice. Results depend on your situation, market and effort; adapt what you learn to your own context.