∴ The total number of people surveyed is 108÷0.54=200 (people),
∴m=200×0. 15=30 (person),
There are 108 people who exercise for 29 minutes or less every day, with the largest number.
∴ The mode of this set of data is: less than 29 minutes;
About 8200× 0.65438+ the school exercises 0 hours a day = 820 people.
So the answer is: 30; 29 minutes or less; 820.