Comment by WhyNotHugo

At first I had to count characters. Over time, it becomes intuitive. In the same way that if someone holds up three fingers you don't count "one, two, three", you immediately perceive that they are holding up three fingers.

For numbers under 10, I usually hit the right amount. For numbers around 30, I might be off by one to five, but move on from then. When I want to remove similar prefixes from multiple non-consecutive lines, I might use things like 31x, go to the next instance (maybe continuing a search with n), and press period.

Honestly though, if you're moving forward 31 characters, there's often an easier approach, like 4w (move forward three Words). Again, at first I had to consciously think about which combination to use. Over time it becomes second nature.

I still use jjjj sometimes. It's imperfect, but at least it's the human that's the limiting factor, and not the software.