How to calculate gst credit

actuualy i had a word with gst helpine they said when u file gstr 3 .there u have to enter business  expenses there they show how much credit is available on that particular business expenditure 

i dont knew wheather it is correct or not

thank you 

manish

I m talking about how much credit we get on buisness expenditure

like if we purchase laptop or took some service so how can we calculate how much gst credit available on that particular laptop or on that service we took for oure buisness

in which return we file these expenditure so we get itc on particular business expenditure