You can set up a number of selections the respondent will be able to make on the image you have displayed. The maximum number of selections is 20.
You can select a color for the border of the respondent's selection.
You can limit the number of points a respondent can select / click. If a respondent exceeds this limit, the latest selection will replace the oldest one:
Once this option is enabled, respondents see a small dot where they click.