How do I convert 8.03 to 08:03 as time and how to calculate the table below

e.g.
Need to work 8 hrs per day
Time in Time out Difference Overtime
Due time
8.03 16.00 ??
?? ??
8.00 15.45 ??
?? ??

When an employee is absent

0.00 0.00 ??
?? ??