How many additional ticks and gridlines can I add to an axis?

A powerful feature in Prism is the ability to add additional ticks and/or gridlines with labels at selected coordinates along the axis. This is done at the bottom of the X or Y tabs of the Format Axis dialog. 

As soon as you enter one, Prism adds a line to that table so you can enter a second. And entering a second, creates a row for entering the third. But there is a limit. With Prism 7, you cannot enter more than 30 additional ticks and/or grid lines. Prism 8 lifts this limit to 100.

Notes

• Prism 7 Mac actually does let you enter more than 30, but this is a bug. While more than 30 ticks or grid lines will show on the graph, the associated label will not. And everything past 30 will get lost if you open the file in Windows. And you may get unlucky and have Prism Mac freeze on you if you try to edit additional ticks past 30.
• The limit is for each segment of an axis. If you make the axis discontinuous, then you can enter 30 additional ticks for each segment. 
• If you want to create regularly spaced grid lines, there is an easier way. On the X or Y axis tabs, set up the spacing for major and minor ticks. Then go to the first tab of that dialog where you can choose to include grid lines at each major and/or minor tick.