What penances do priests do for sins they absolve?

I watched [this video](https://www.youtube.com/watch?v=YiVjwlUO9Sc) by Fr. Mike Schmitz, near the end he says that after a long time of not going, he made a general confession and was given one Hail Mary as penance and the priest said that he was going to fast for 30 days for him. He then said that this is normal and the catechism says that priests have to do penance. I'd never heard this before, but I did find it in the catechism > The Church, who through the bishop and his priests forgives sins in the name of Jesus Christ and determines the manner of satisfaction, also prays for the sinner and does penance with him > > [CCC 1448](http://www.scborromeo.org/ccc/para/1448.htm) So, does that mean, the priest keeps a tally of the penances or priests in general are called to do penance as a normal part of their duties as priests? Do priests who spend more time hearing confession (or hear particularly grave sins) have to do more penance?