There is a deduction of 15% from GST amount charge as administration fees by IRIS Global Blue (an appointed agent by Royal Malaysian Customs Department to implement a Tourist Refund Scheme), therefore no full amount to be refunded.
Please see below example for your further understanding.
Total Invoice Value Include GST = MYR300
GST amount = MYR16.98
Administration Fees = MYR2.58 (MYR16.98*15%)
Tourist Refund Amount = MYR14.40