dear community

can someone in the community assist me to this task..

I want to fill in a cell with time - 15 minutes - but whenever I type in 15
and I formatted the cell in "mm" format, the value just turned into "01".
When I go into that cell in Edit Mode, it shows me some kind of date format ??

how can I enter a cell, say, just wanting it be in seconds or in minutes or
in hours.

lastly, hope my question is not too long.....

I wanted to do an autofill a column of cells by a constant time value of (15
minutes), how can I do that ?

thanks community for any assitance render and much appreciated for that :)


--
oldLearner57