How'd they do that?

ok, Anybody out there able to figure this out?



1. Key into the calculator the first 3 digits of your phone number (not
area
code).

2. Multiply by 80

3. Add 1

4. Multiply by 250

5. Add last 4 digits of your phone number

6. Add last 4 digits of your phone number again

7. Subtract 250

8. Lastly, divide by 2

Is this your phone number???

If you can figure this out, please explain how the arithmetic works!!