Most layers type layers have a subsection called Info Bubble in the Appearance section. This control is what is shown when the mouse is passed over a region or point. The standard behavior is to display the dimension value (if it is set in the information) and the value of the measures (in this case Collisions), as shown in the following screenshot:

Let's see how to configure this using the following option:

You can enable/disable the bubble by adjusting the Show Info Bubble checkbox. You can also enable/disable the default Format Numbers option, as shown in the preceding screenshot.

In our case, the Format Numbers option is important, because our zip codes are numeric. Take a look at the changes in formatting shown in the following screenshot: