Daneton Power started the fire on June 6, and caused £1,949 of damage.
"There was a lot of smoke and a scorch mark on the floor," said prosecutor Kate Beardmore.
"It looked worse than it was but it is a fire he started, and the starting point is nine months."
Tim Haines, mitigating, said: "I have analysed the arson guidelines and this is clearly beyond the sentencing powers of the magistrates.
"It is potentially aggravated by the location. But there was no intent to create issues with a third party.
"It was a cry for help as he was under threat by other inmates. Ultimately he was transferred."
Power, 22, currently a serving prisoner at HMP Moorland, Doncaster, admitted arson when he appeared, via a video link, at Mansfield Magistrates Court, on
He will be sentenced at Nottingham Crown Court, on November 21.
For more cases from Mansfield Magistrates Court, click here.