I am an American studying abroad in Germany, but I want to spend up to 90 days as a tourist in Spain following the end of my program and the expiration of my residence permit.

I entered the Schengen zone on the grounds that I have US citizenship and can therefore enter without a visa and stay in Germany for up to 90 days while applying for a residence permit. However, I do not know if the two months that it took me to officially receive my residence permit count as ~60 out of the 90 days. I do know however that time passed within the period of the res permit does not count towards the 90 days, as other posts have pointed out.

The main thing I want to know is if my residence permit retroactively covers that two-month period that passed before I officially received it (I was already applying for it upon arrival, but it got delayed and so the sticker in my passport officially says the term is March-June, even though I arrived in January). If so, I would have never started an 180 day cycle and can therefore just make a stop in the UK and get a re-entry stamp to Spain to begin my 90 days as a tourist.