can't calculate prediction with linest_m and linest_b

[bentley32]

Hello all,

I dont know why i cant calculate the prediction with my formula,

I do have 2 dimension, yearmonth which is the registration date, and Dim which is the billing date months M+1 M+2 and so one

this is my formula 

if(REGROUPEMENT or REGROUPEMENT=0,REGROUPEMENT,
linest_m(total <[registration_date.autoCalendar.YearMonth]> aggr(if(REGROUPEMENT or REGROUPEMENT=0,REGROUPEMENT),Dim,[registration_date.autoCalendar.YearMonth]),Dim)*only({1}Dim)

+linest_b(total <[registration_date.autoCalendar.YearMonth]> aggr(if(REGROUPEMENT or REGROUPEMENT=0,REGROUPEMENT),Dim,[registration_date.autoCalendar.YearMonth]),Dim))

what i need is to calculate with the behaviour of the DIM (the billing dates) the future billing dates of the next registration date

this is my table and what i need to get filled and what i got ...

what need to get filled : 

How it got filled wrongly : 

Thanks for your help

[bentley32]

anyone 🙂