Today I had to extract in excel a value from a text which is always the same. Only the value is different.
Text in the cell is actually a rear backup output showing backup time: "Archived X MiB in X seconds [avg X KiB/sec]"

Ok, let's give an example.

Extract 289 from "Archived 2900 MiB in 289 seconds [avg 10275 KiB/sec]"

This text is in cell A2 and the result will be in B2 (we will put the formula below there).
The needed formula is: =MID(A2,SEARCH("in",A2)+2,SEARCH("seconds",A2)-SEARCH("in",A2)-2)

That's about it but what if A2 does not have the text added yet? You will have errors all over the place.
No worries, include all in =IFEROR(), "") which means If there is an error, show nothing:
=IFERROR(MID(A2,SEARCH("in",A2)+2,SEARCH("seconds",A2)-SEARCH("in",A2)-2), "")