Require formula to return value of hours worked in tenths.

I am working on an hour recording sheet that will be used by future interns at my place of work. I have hit a road block and want to make this spreadsheet as autonomous as possible.

What I have so far is a setup where the user enters their start time, stop time, and lunch duration (all in military). Another cell then subtracts the start time and lunch duration from the stop time for example:

"Start Time:7:00
Stop Time: 14:00
Lunch Duration: 0:30

The function then takes 14:00-7:00-0:30=6:30"

This is good and all but our emplyer requires us to enter our hours in tenths of an hour. For example:

The table we use is:

TIME MUST BE ENTERED IN TENTHS OF AN HOUR
___Minutes_______Tenths__________Minutes___________Tenths
_____0-5_________0___________30-35___________0.5
____6-11________0.1___________36-41___________0.6
___12-17________0.2___________42-47___________0.7
___18-23________0.3___________48-53___________0.8
___24-29________0.4___________54-59___________0.9

So the input of the above 6:30 would end up being 6.5.

Does anyone know how to write a function that will return the hours in this form? Any help is much appreciated. Thank you!

If you multiply the result by 24 and format the cell as General, you will get 6.5 (when 6:30 is time result).

You can use TRUNC()

e.g =TRUNC(A1*24,1)