UOB ATM in Singapore

I withdrew S$100, and the DCC offer appeared as 1 SGD = 0.78181 USD (3.99%) for $78.18. There were buttons at the bottom with both SG and US flags and read, "Proceed without conversion," and "Proceed with conversion." I declined DCC, and the pending transaction showed as $75.18, which matches the 3.99% markup.