By Julie J. -
Stroke count is the number of strokes you take to complete a lap. Swim tracking devices typically only count the number of strokes made with the arm that is wearing your swim tracking device. This is because the tracker can only measure what it knows to be true. There is no way for the tracker to measure what your other arm is doing.
For example, if you swim one length with the Swim.com app on your Pebble watch and the Pebble records 11 strokes, this would be interpreted as 22 total strokes to cross the pool. However, if you end the length with the same arm you started with, the total stroke count for the length could be 21 or 23.