Another swimming miscalculation

Unfortunately I have to wait until my next swim time trial to confirm that I am improving significantly on my swim. As I was getting towards the end of my swim I was having a little trouble with cognotive reasoning (oxygen debt). I remember telling myself 150 yards to go. Then I remember thinking is it 150 yards after these laps or do these laps include the 150 yards. Like always, I tagged on 50 yards rather than short the swim. My time was 14:23 which would make this one of my slowest 800 yard time trials in recent history. I am fairly certain that I swam 850 yards which then turns this into my fastest time trial in recent history. I felt really good on this swim even though I was sore all over from the prior day's sessions. I feel real confident that this was a good swim - I know I pushed hard and my stroke felt strong. After I caught my breath enough to funtion a little bit I checked my HR and it was still over 160. Next week is a 500 yard TT. I know I can count to 20!