To compare the data within a time period, you can go to 'WiFi Analytics' and then 'Compare Statistics' on the left side of the page. First, you should filter the venue, its floor and date range and click 'Apply' to get different insights about your business. For instance, you may be interested in comparing your statistics in the last 5 days or weekly in the past month.
On the graph, you will be seeing 4 lines representing different information as following; total visits as blue, average dwell time as green, total visitors as orange, and new visitors as black. By hovering over breaking points of each line, you can see the numerical values for the particular date.