https://www.chess.com/blog/News/chess-com-dev-update-april-28-2017
and
https://www.chess.com/blog/News/chess-com-dev-update-may-26-2017
It means you took longer than your Target Time to complete the puzzle but were very close to it. Those links give some explanation on how things work.
The puzzle rating increase and decrease when they are failed or solved. The amount of points the puzzle is worth is a rating calculation based on the tactic's current rating versus yours, though there is a finite range. And the average solve times are based on how long it has taken others to solve the tactics.
I do the daily tactics puzzles.
What does the % measurement mean?
e.g. my tactics score after solving the last of the 5 puzzles is 928 (+9) 90%
What is 90%?
The %age changes up and down from puzzle to puzzle.
I guess the points you score depends on how quick you solve the puzzle so maybe 90% means that there was a maximum possible 10 points for solving that puzzle in under the target time?
Would also be curious to know how the points scored is affected by variables. I guess harder puzzles are worth more points (i.e. rating number on the puzzle)? Solving the puzzle faster is worth more points?
Is the rating affected by the pass rate? i.e. if most people are failing a puzzle it must be hard
Is target time affected by attempts by previous users or is it just an arbitrary estimate by the person who put the puzzle together?