A scale is series of numbers placed at fixed distances on the side of a graph.

I think it's the horizontal axis or y-axis. The limit of the axes (ie the maximum number that can be represented) is called the values, and the fixed points where the numbers go are gridlines. I hope this is right - you can find more information here. The pull-down menus are really good.

Scale

Scale

Category

The blank is a series of numbers placed at fixed distances on the side of a graph