The WAN Utilisation Distribution Report uses 'mode=>MAX' to ensure it is using the most accurate summarized data available for the task at hand.
NMIS version 8.6.8G (and newer) export data using both 'mode=>AVERAGE' and 'mode=>MAX'.
The best way to understand ther difference between 'mode=>AVERAGE' data and 'mode=>MAX' data is to use NMIS version 8.6.8G (and newer) export data functionality and compare the returned data for 'mode=>AVERAGE' and 'mode=>MAX'.
Open NMIS, login and choose the desired node we wish to work with - in the example image below we have chosen BANORTE_CAJ_N40051_NIHON_PLAST_II_RT01 highlighted in blue:
NMIS will then open a form for that desired node - to get NMIS node.pl to open click on one of the graph images - for example the graph highlighted in blue on this image: