The entire number you wanted to be. The picture shows 1 way, which is left to right going all the way to 15. You can make go up to 7 if you do not want the last few frames to appear.
The file name: theexamplename_1w7.png = This means the engine is going left to right to animate it and will stop at 7. if you put it on loop it will repeat 1-7 for the whole game.