Calculate interval and mark it in another column

Hello there,

I need to calculate an interval. Therefore I take a point in time, subtract 2 seconds and add 10 seconds.

e. g.: With a point in time of 8.5 I have an interval from 6.5 to 18.5 seconds.

Now I need to mark this interval in another column. So with an interval from 6.5 to 18.5 it would look like:


6.2
6.7
7.8
13
15.7
18
19


What is the most efficient way to do this? How can I calculate the interval and mark the corresponding area?


Thanking you in anticipation