This is working for some of the numbers I plug in, but not for all.

Example:

I plug in 700 in A5. My answer for A6 should be 6.54.

700 divded by 2 = 350 which would mean 2.54
350 divided by 250 is 1.4 (round to the next whole number (2) 2x2 =
4.00
So then I add 2.54 + 4.00 to get 6.54

Which the formula mentioned I get: 5.34.

Could it be the rounding part that is getting me?

If I plug in 1,000 in A5 I should get 6.24 in A.
With the formula I get 6.54.

Another Example:
1000 divided by 2 = 500 which would mean 2.24
500 divided by 250 is 2 (2x2 = 4.00)
So then 1 add 2.24 + 4.00 I should get 6.24.