Clearblue Ovulation test


I have a Clearblue ovulation advanced test. Problem is of course my period wants to act up so now I don't know when to start. Friday the 11th had lightest red/brown spot, Saturday 12th nothing, Sunday 13th full on AF. Would I use fri or sun as cd1? I heard this test is real picky so trying to get it right 😟

Also anyone have any lucky with it?