If I have a lot of times to enter in m:ss format, I find it more
convenient to enter them as m.ss and then have a formula to convert
this format. If you entered 1.1 in cell A1 (meaning 1:10 - you don't
need to enter the zero), then this formula in B1 would give you 70
seconds:

=INT(A1)*60 + MOD(A1,1)*100

The formula can be copied down column B and then the times can be
entered in decimal in column A. You can pre-format column A to 2 dp so
the times look similar.

Hope this helps.

Pete