You can change the size and spacing of the timing marks by selecting the timing line and clicking the Properties button. This window opens:

Timing marks are always numbered from the top (portrait pages) or left (landscape pages).

In Edit mode, you can type in the values for each timing mark, or set an identical universal value for a dimension by clicking either the Set sizes or Set spacing button. That dimension is applied to all timing lines.

In Select mode, you can select a range of values by dragging with the mouse and clicking either Set sizes or Set spacing to set the dimensions for the selected range.

This shows space reduction on the first set of timing marks.