These compare the volume over the last minute to the volume expected in a 1 minute period. The result is always a percent.
It doesn't say how the expected volume value is calculated. At a guess, it might be the average for the session start-relative m-minute interval for the last n days, possibly taking into account other variables like day of week.
My assumption that the vol % in 10min is based on the previous vol % in 10 min was completely off but that's how the description seems to read.I don't, either.
I suspect that without knowing what your software is and/or seeing the manual, it isn't going to be possible for anyone to answer you definitively.
The problem is the description is hiding vital information on purpose. No idea what 400 is trading 4x normal more of what? The average X min interval? In how many days?
Maybe, someone who's been using TI longer than me can chime in but if not I pretty much got an idea of how to use it. I'll just never know for sure how the formula is calculated.