Now the y-axis.

1. Count the number of lines the axis has: count like moving on a board game, don't count the first line. On this graph there are 18 lines on the y-axis.
2. Determine the maximum value to be plotted on the y-axis. For this data the maximum volume was 72 mL.
3. Set up a ratio of maximum data value to number of lines:

1. Again, you do not want to label every line. So let's label every 3 lines, that would be 12 mL for every 4 lines and will end with 72 on the last line. Most dependent variable data is not going to follow an exact interval like the independent variable, which is set to be at specific intervals. As a result there is usually no reason to fiddle much with the scale one you find one that works with the number of lines you have.
2. Scale the axis:

Now plot the data points on your graph.