How ray tune hyperband schedule generates and stop trials?

I use ray tune HyperBandForBOHB function as schedule, the optimization method is BOHB, and the setting is
bohb = HyperBandForBOHB(
time_attr=‘training_iteration’,
max_t=5,
reduction_factor=3,
)
I set num_sample=50, I want to know how it calculate each round train how many trials?
here is the log:
Round #0:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}
Round #1:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}
Round #2:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}
Round #3:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}
Round #4:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}
Round #5:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}
Round #6:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}
Round #7:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}
Round #8:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}
Round #9:
Bracket(Max Size (n)=1, Milestone (r)=3, completed=100.0%): {TERMINATED: 3}
Bracket(Max Size (n)=2, Milestone (r)=5, completed=100.0%): {TERMINATED: 2}

it seems each round has 1 trail training 3 iterations, 2 trial training 5 iterations, I want to know how adjust these setting, I think is related to max_t and reduction_factor, but how the relation between num_sample=50, max_t=5 and reduction_factor=3?