Calculating a percentage of a given time span

I have a weekly data report that is generated with one column containing how long a given task took (in hours) and I need switch that to minutes and then I need to discover the percentage time of the week (business days so 7200 minutes) it took to complete the task.

I converted the hour to minutes by just going to Format-->Number and doing a custom entry of [m], but when I type in the simple formula to get the percentage =A2/7200 I'm coming back with very faulty data.

The problem I'm encountering seems to stem from the fact that even though my time column visibly appears to have changed to minutes when I click on a cell and look in the formula bar it reads as "1/3/1900 1:30:53 PM" (the serial date I believe?) and then my average formula is using that to calculate the percentage, which is not working at all.

Is there a way I can make the time presented to me as the serial date have the actual minute value so I could use the data in a formula?

Let's see if I can clear this up a bit:

The company I work with provides tech support 24/7/365. A customer of ours wants to know when one of their servers goes down how long (in minutes because that's what they asked for...don't know why they want minutes in particular) it takes us to restore it and they also want to know how long the server was down for the week (in percentage format). The current date period of the report I'm running is a Monday-Friday report, hence the 5 days and 7200 minutes.

I have a company program that records the amount of time (in a hh:mm:ss format) it takes to restore service. My problem is that when I export that information to an Excel spreadsheet, Excel is not reading 8:24:25 as 8 hours 24 minutes and 25 seconds, but rather as 8:24:25 AM. i.e. it's giving it a time stamp and not reading it just as a set number of hours, minutes, and seconds.

I didn't think this would matter, but I cannot get my formula to give a correct answer when it has that time stamp on it and I need to know if it's possible to get rid of said time stamp.

I've attached a sample spreadsheet that lists a few examples. Column A is the original data generated in hours, Col B is that data converted to minutes, Col C is the percentage I get when I use the =B2/7200, and Col D is the percentage I get when I manually typed in the number =504/7200

I hope I better explained my problem and thanks for the help!