Adding Trendline to Line Chart

[jbalfe11]

I have a data set with data from Nov-2014 thru Dec-2015. I have a line chart where I sum the total seclusion time (if the number is > 0). I added a second line to chart a trend line (expression for that line is below). It looks like it works except for the first couple of months which are way off? I tried adding the expression in the Add Ons > Reference Lines section but I got no results for that. Any idea why the data is so off for the first couple of months? Please see attachment for screen shot and qvf file

linest_m(total aggr(if(sum({<[TotalSeclusionHours] = {'>0'} >} TotalSeclusionHours),sum({<[TotalSeclusionHours] = {'>0'} > }TotalSeclusionHours)),Year-Month),Year-Month)* 

only({1}Year-Month)+linest_b(total aggr(if(sum({<[TotalSeclusionHours] = {'>0'} >} TotalSeclusionHours),sum({<[TotalSeclusionHours] = {'>0'} >} TotalSeclusionHours)),Year-Month),Year-Month)