The "Create Event Wizard" will guide you through the setting up of a new event file. The "wizard" is shown when you use the menu item File / New Event File.
This page is shown only if - on the previous page - you selected to use the same map with two printout scales, or two maps of the same area.
Here, you can configure if the control circles for the two printout scales should be linked closely so that if you cut the circle on one canvas, this is reflected on the other canvas.
Additionally, you can configure if you want the control circles to be scaled proportionally with the printout scale, so that if you for example use 1:15.000 and 1:10.000, the circles will be larger on the 1:10.000 map than on the 1:15.000 map.
The selection on this page affects the control settings for Canvas 1, and possibly Canvas 2 (if two maps are chosen). You can later change the settings by using this dialog: Canvas / Controls - Setup Controls Dialog