Time and average help

[Henrygruby]

Hello I am having trouble with some running times.

I have 29 mins 40 secs and 31 mins 28 secs but the only way I can get them to stay looking like 29:40 is to have the format as text because if I put it as mm:ss it changes the time for some reason.

Secondly if I try to get an average in the usual manner for these two numbers it won't allow it, probably because they are formatted as text and not mm:ss but how do I get around this?

Thanks.

[oeldere]

show the file, so we can take a look at it.