You can use up all 150 slots, with either 7 or 8 people per team per day, as follows:
Day 1:
Team 1 {1,2,5,6,7,8,9,10}
Team 2 {1,2,3,4,5,6,8,10}
Team 3 {1,2,4,6,7,9,10}
Team 4 {1,2,3,4,6,8,9}
Team 5 {1,2,3,4,5,7,8,9}
Team 6 {2,3,4,5,6,8,9,10}
Team 7 {1,2,3,5,6,7,8,9}
Team 8 {1,3,4,6,7,8,10}
Team 9 {1,3,4,5,6,7,8,9}
Team 10 {1,3,4,5,7,8,9}
Team 11 {1,3,4,5,6,7,8,10}
Team 12 {3,4,5,6,7,8,9,10}
Team 13 {1,2,4,6,7,9,10}
Team 14 {2,3,5,6,7,8,9,10}
Team 15 {1,2,3,6,7,9,10}
Team 16 {1,4,5,7,8,9,10}
Team 17 {1,2,3,5,6,7,9,10}
Team 18 {3,4,5,6,7,8,10}
Team 19 {2,3,4,5,7,8,10}
Team 20 {1,2,5,7,8,9,10}
Day 2:
Team 1 {1,3,5,6,7,8,9,10}
Team 2 {1,3,4,5,7,9,10}
Team 3 {1,3,4,7,8,9,10}
Team 4 {3,4,5,6,7,9,10}
Team 5 {3,4,5,6,7,8,9}
Team 6 {1,2,3,4,5,6,8,10}
Team 7 {1,2,3,4,5,7,8,10}
Team 8 {1,3,4,5,8,9,10}
Team 9 {1,2,4,5,6,9,10}
Team 10 {1,4,5,6,7,8,9,10}
Team 11 {2,3,5,6,8,9,10}
Team 12 {1,2,3,4,6,7,8,9}
Team 13 {1,2,4,5,6,7,10}
Team 14 {1,3,4,5,6,7,8,9}
Team 15 {1,2,3,4,5,6,7,8}
Team 16 {1,2,3,4,7,8,9,10}
Team 17 {1,2,4,5,6,8,9,10}
Team 18 {1,2,3,4,5,8,9}
Team 19 {1,2,3,4,6,7,9}
Team 20 {1,2,3,4,6,7,8,10}
Day 3:
Team 1 {1,2,3,4,6,7,9,10}
Team 2 {1,3,5,6,7,8,10}
Team 3 {1,3,4,5,7,8,9}
Team 4 {1,2,3,4,5,6,9,10}
Team 5 {1,2,4,5,6,9,10}
Team 6 {1,2,3,5,6,7,9,10}
Team 7 {1,2,3,4,5,6,8}
Team 8 {1,2,4,5,7,8,9}
Team 9 {2,3,5,6,7,8,10}
Team 10 {1,2,4,5,6,8,10}
Team 11 {1,3,4,5,6,7,8,10}
Team 12 {1,2,3,5,7,8,9,10}
Team 13 {1,2,3,4,5,6,8,9}
Team 14 {1,2,3,4,5,6,7,10}
Team 15 {1,2,3,4,6,8,10}
Team 16 {1,3,4,6,7,8,9,10}
Team 17 {1,2,4,5,7,8,10}
Team 18 {1,4,5,6,7,8,9,10}
Team 19 {1,3,5,6,7,8,10}
Team 20 {1,3,4,5,6,8,9,10}
Day 4:
Team 1 {1,2,3,4,5,6,9,10}
Team 2 {2,3,4,6,7,8,9}
Team 3 {1,2,5,6,7,8,10}
Team 4 {1,4,5,6,7,8,9,10}
Team 5 {1,3,4,5,6,7,9,10}
Team 6 {1,2,3,7,8,9,10}
Team 7 {1,2,5,6,7,8,9,10}
Team 8 {2,5,6,7,8,9,10}
Team 9 {1,3,4,5,7,8,9,10}
Team 10 {1,2,3,4,7,9,10}
Team 11 {1,2,4,7,8,9,10}
Team 12 {1,2,3,4,6,8,9,10}
Team 13 {3,4,6,7,8,9,10}
Team 14 {1,2,3,4,5,7,8,10}
Team 15 {1,2,4,5,7,8,9,10}
Team 16 {1,2,3,4,5,6,9}
Team 17 {1,3,4,5,6,7,10}
Team 18 {2,3,4,5,6,7,8}
Team 19 {2,4,5,6,7,8,9,10}
Team 20 {1,2,4,5,6,7,9,10}
Day 5:
Team 1 {1,2,3,4,5,7,8,10}
Team 2 {1,2,3,5,6,7,8,9}
Team 3 {2,3,4,5,6,7,8,10}
Team 4 {2,3,4,7,8,9,10}
Team 5 {2,3,5,6,8,9,10}
Team 6 {1,3,4,5,6,7,9,10}
Team 7 {1,3,4,5,6,9,10}
Team 8 {1,2,3,4,5,6,7,8}
Team 9 {1,2,4,5,6,7,10}
Team 10 {1,2,3,5,6,8,9}
Team 11 {1,2,5,6,7,8,9,10}
Team 12 {1,2,5,6,7,8,9,10}
Team 13 {1,2,3,5,6,7,8}
Team 14 {2,3,4,5,6,8,9,10}
Team 15 {1,2,5,6,7,8,9,10}
Team 16 {1,2,5,6,8,9,10}
Team 17 {1,2,3,5,7,8,9,10}
Team 18 {1,2,3,5,7,9,10}
Team 19 {1,2,3,5,7,9,10}
Team 20 {1,2,3,5,6,8,9}
I obtained the solution via integer linear programming, and $8-7=1$ is the minimum range of team member counts per day.