For very short intervals NP can be less than average power. Furthermore, for anything less than 20min NP is generally considered invalid. That said, with your 10s intervals, it is expected that your NP be lower than the average power as well as meaningless.
The search results seem to match your criteria. Are you saying that the average power for interval 1 was not 537W, but instead that the peak for that 10s was 537W?
Also note, that if you do a search for 10s intervals above 500W, it will not necessarily match the intervals of the TR workout you were doing. If the TR workout has 10s intervals, the summary will show the average power for those exact 10s. Meanwhile, the search will show 10s which could start before or after the actual TR intervals. Click on the “+” to see the exact start/stop time for the search result.