It would be easier if you enter your time in different increments. For example...10:15 becomes 10.25....10:30 is 10.5.

You are mixing hours and minutes the way you have it right now.

You could get fancy and divide by 60, etc. but that is the easiest way.

I'm not a wake yet....one more edit...that is why attorneys and the like bill in 6 minute increments....1/10th of an hour....