linestx

I am confused how the LINESTX function works within a group.  The first screen shot is of a matrix showing that there is only 1 k1 record for any given l0 group.  The second screen shot is of a matrix where I am trying to display the LINESTX column of R2 (DAX formula below).  The second matrix only has l0 as part of the row group and therefore should be providing the LINESTX function a unique value for the LINESTX x-value parameter of [k1].  

r2_fk01 =
var l = LINESTX('fk01 mx',[max pct],[k1])
return SELECTCOLUMNS(l,[CoefficientOfDetermination])