Riddle: The Missing Camel

A simple peasant has bought a number of camels and is taking them to his farm.

As he rides contentedly along he counts them – he counts 29. He was sure he had bought 30 camel so in alarm he jumps off his camel and counts the camels again.

To his delight there are 30. Half an hour later he counts his camels and once more there are just 29. Confused he climbs off his camel and counts again. Once more there are 30.

Can you explain?