Error while finding Count of Members between range:invalid argument in function [@_BPROC]

Summary:

Encountering invalid argument in function [@_BPROC]

Content (required):

Hi All,

Here we are trying to find count of Members between Start Month & End Month in a year & store in a variable, use the variable to divide the amount equally.

CountMonth=@COUNT(SKIPMISSING,@XRANGE("FY23"->@MEMBER(@CONCATENATE("HSP_ID_",@HspNumToString("P_Start Month"->"BegBalance"->"No Year"->"No Funding Source"->"No Project Element"->"No Resource Class"))), "FY23"->"Dec"));

"OPF_Load"->"FY23"= "FY23"->"BegBalance"->"OPF_Direct Resource"/CountMonth;

No errors while Validate & Deploy, getting below error while executing the rule

Please share your thoughts on this.