Mileage Reimbursement Formula (custom calculation) Issue with the decimal points

We have a Mileage Reimbursement form. I was tasked with figuring out how to automatically calculate the miles due. Below is what I did to make it calculate.

Now the problem is that when someone puts in decimals it goes into some really long decimal.

But it's only some of the decimals and it doesn't matter where on the column the decimal is put it will do it.

Can some please tell me what I should do? Thnnk you!