How did 10,000 Russian prisoners die in the Ukraine war?

The head of Wagner, a mercenary group in Russia, has said that 10,000 prisoners sent to fight in Ukraine have died.
According to the French news agency AFP, Wagner’s head, Yugozin Prigozhin, visited Russian prisons last year and told inmates to join his group to fight in Ukraine, and if they returned alive, they would be killed.
These prisoners are said to have been used as fodder in Ukraine, and the Wagner group was among the worst killed.

“I took 50,000 prisoners, 20 percent of whom were killed,” the head of the Wagner group said in a video statement.
He said a similar proportion of those who contracted with Wagner were killed, but did not specify the number.
Russia’s military said a few days ago that the city of Bakhmut in eastern Ukraine had been captured, but Ukraine said fighting was continuing.

Wagner’s head criticised the Russian leadership for the heavy loss of life and said that the Russian Minister of Defence and the Chief of the General Staff are incompetent. There are tens of thousands of relatives of those killed, and the number is likely to reach hundreds of thousands. We cannot hide from it.

He asked Russia’s military elite to send their children to the war front.
Yugozhin Prigozhin, who is considered to be close to the Russian president, said that his people would withdraw from Bakhmut by June 1 and hand over Kandol to the Russian army.
In early May, the United States said that 20,000 Russian soldiers had been killed and 80,000 wounded in eastern Ukraine, particularly Bakhmut, over the course of five months.