I got an error below highlighted pink colored code...
if(len(RegFromDate)>0 andlen(RegToDate)>0,
sum(aggr(sum({<REGISTERED_DT_Num={">=$(RegFromDate) <= $(RegToDate)"},STATUS = {'Settled'}, TYPE_CLM={'Star Care Plus 4'}, STAR_CARE_SHARE_PART=-{0},X_PRODUCT_LINE=>} WOClaimed),Dealer_Alias,NAME_DIV,WRNTY_NUM)),
sum(aggr(sum({<STATUS = {'Settled'}, TYPE_CLM={'Star Care Plus 4'}, STAR_CARE_SHARE_PART=-{0},X_PRODUCT_LINE=>}WOClaimed),Dealer_Alias,NAME_DIV,WRNTY_NUM))
The expression editor doesn't understand -= and will show the expression as incorrect. But that's a bug in the expression editor. It does not necessarily mean that the expression is incorrect and will not work.