summarising data from dataset (tally Numbers Based off user)

For my hiking website, i would like to have them submit and log their own hikes. I have this running and it feeds into a data set that displays on a repeater but as part of this i would like to also display their lifetime stats such as total kilometers hiked. Is there any way to tally up data submitted by solely that user to give me a total number. I have set up a number field and they can submit to them just don’t know how to tally it all up.

If you could help me that would be great. (please provide code example or explanation)

I have previously bought this issue up but was unable to find an answer, i can provide the basis for some code that someone helped write for this function but I think it doesn’t work.

Thanks for the help, Josh