Default space for all subdashes is 0. This means that every subdash touches each other. In case of single dash, it means that the dash takes whole space available. On the figure 1 you can see the dotted dash with space 0:

Figure 1: Dash with space 0

Figure 2: Dash with space 1

Figure 3: Dash covers only 1/7th of the total weight

Related to the space issue, notice that the space affects the fill area of the box or text frame (on the following screenshot, you can see that there's a space between the rule and the fill: it is created by the space = 3), but it does not create margins of the text - these are handled by the tags in the text (if any).