Big Dad Mug doesn't contain the promised mills

On Monday, 21 September 2015, we went to Hooters Emperors Palace for a few beers and a meal. At the waitress's recommendation we ordered the 1 litre Big Dad beer at R44.00 a mug. When the beer arrived, we asked the waitress if the mug indeed contains a litre of beer and we were assured that it is the case. We then proofed to her that it only holds about 850 ml of beer and not the 1,000 ml as promised. The barman did not want to comment on this. I would like to bring this to everybody's attention as Hooters are not honest in their dealings with the beer drinkers that order the Big Dad. We are done in by 100 to 150 ml per beer - I wonder how many litres of beer are \saved"...."""