Formula repeating same results when applied to all rows

I run into this a lot. I'll execute a formula in my first row, then double click the bottom right to continue the formula for all rows.

When I do this, I'm repeating the same value for each row. Am I doing something wrong?

(okay now when I went back, the values are correct. Why would they initially be incorrect? I've had this happen numerous times)

most likely your sheet is on manual calculation. when you copy formulas when it is on manual calculation you see the same results, after pressing F9 all formulas will calculate correct result.

you can read on manual vs automatic calculation settings here:
https://support.microsoft.com/en-us/...8-67124f6bcce4