Riddler's Back!- I know your phone number...

Alright, folks. Get a calculator! Here's a trick that'll blow your minds! (This does not work for 8-digit numbers, sorry Australians...)

Put the first three digits of your phone number (NOT THE AREA CODE!),
Multiply that by 80,
Add 1,
Multiply that by 250,
Add the last four digits of your number to that,
Add the last four digits of your number-- again,
Subtract 250,
Divide by 2;

Look Familiar?

Read on, and give me a thumbs up if you enjoyed!!