The new REST API Guide has more information on dwellBreakdown resource.
The Cisco Connected Mobile Experiences REST API Guide, Release 10.3 updated on 6/20/17 is found at http://www.cisco.com/c/en/us/td/docs/wireless/mse/10-3/api/b_cmx_103_api_reference.html
Seems the link is missing when looking under the old Programming Guides
From the apidocs CMX REST Documentation
You may set quantitatively what "light", "medium", or "heavy" are in terms of count.
Numbers would be the wireless client count.
Data - has groups of 18 representing 18 of 24 hours. Notice
"dataFreshness": "2017-06-06T17:43:53.908+01:00", is time of report
TimeRange - The time window of interest on each day. If "now" is
given, the granularity can only be a tag name or heterarchy level.