thanks for your answer! yes i have also read this solution in an other old post, but it did not work with me. my document unit is meter, so i just divided 1 sq m. Unfortunately it shows for example: 20 sq msq m l/s
BUT, i finally find a way to get it! i have to define a record "1 sq m" in record format and then use this record to be divided by AREA. Then it works! Just notice, DONT use "document unit", use "square meters".
i still don't know why it has to be so complicated:(
but at least, it works:)