ERP component mean


I would like to extract mean amplitude values for my components (P1, N1, P170).
I have tried the method : average --> average time --> selecting window and mean.

However, it seems like it didn't work correctly. For instance, most of the mean for the channels of P1 are negative values, which shouldn't be the case since P1 is a positive peak. I think it just gave me the mean for the signal as a whole (taking in account also the negative peak).

Is there any way to extract the correct means for each of my components ?

Could it be an issue of referencing?
Can you share some relevant screenshots? (raw data, montages if any, the process that you are running, the result, etc)