I did not set the correct F0 / lethality profile before starting the logger: do I have to redo the test?

The lethality analysis profiles (refer to this FAQ) for the calculation of lethality based on the parameters set in the software and the data recorded by the data loggers, have effect only on the downloaded data, both when downloading from the currently connected logger, and when data is opened in the archive.
Therefore, it is not necessary to have set the correct profile for the process you are about to perform before starting the loggers, just set it when you go to analyze the data. If you have data in the archive and select different analysis profiles in Configuration and reopen those missions, you will find different lethality values.