Week 8 by mistake

I ran R2W7 the day before yesterday and  was looking forward today to my "last" 25 minute run before I started week 8 which I was a bit apprehensive about. After my injury a few weeks ago, the most I could run was 25 mins. But I couldn't find week 7 on my app. It had disappeared! So I ran week 8 - it was hard but I did it !! But how come the last 5 minutes of a run is always slower than the 5 min warm up ?