[Freesurfer] -refeventdur in mkanalysis-sess?

Hi FreeSurfer Team,

I was wondering if you could provide a bit more clarification on what the "-refeventdur" flag is referring to in the mkanalysis-sess command? The description in the help screen states it should be the "duration (sec) of reference event for scaling." I am unsure what the "reference event" is. I couldn't find any additional info on the listserv, and the two examples I saw from tutorials used a value of "4" and another used a value of "16". Any clarification is greatly appreciated! Because the help for the flag is listed under the "Assume a shape" header, does it have something to do with the HRF?

Thanks so much! Tori