string.addCommas (10249)
"10,249"
string.addCommas (999999)
"999,999"
n1 = string.addCommas (49527);
n1 = n1 + 3
"49,5273"
Note that the + operator acts here a string concatenator since the original value has been converted to a string.
string.addCommas ("98765")
"98,765"
Note that the argument is a string enclosed in double quotation marks; Frontier coerces it to a number.