"A lie detector" joke

An Englishman, an American and a Sardarji are called upon to test a lie detector.
The Englishman says:
"I think I can empty 20 bottles of beer".
BUZZZZZZ, goes the lie detector.
"Ok", he says, "10 bottles".
And the machine is silent.
The American says: "I think I can eat 15 hamburgers".
BUZZZZZZ, goes the lie detector.
"Allright, 8 hamburgers".
And the machine's silent.
The Sardarji says:
"I think...",
BUZZZZZZ goes the machine.