10 players was a guide based on even distribution. 6 players in Rounds 1 - 6 and 4 players in Rounds 7 - 10. Helpful for planning a strategy. Reality is obviously different with different strategies being employed.
“the sum total of contracts in the first year must not fall below the sum of the average salaries”
Let's say Team X has won 6 players at a $1M each (average salary) for a total of $6M. They can structure the contracts how they like, within the 50% margin, front or back end or a variation of those strategies. Team X's 2020 structure might look like this:
Player A: $1,500,000 (max)
Player B: $500,000 (min)
Player C: $1,200,000
Player D: $800,000
Player E: $1,100,000
Player F: $900,000
Total:____$6,000,000
There is flexibility, however you have to pay the full price for your players in Rounds 1 - 6.
NB. This does not apply to Rounds 7 - 10. This is where you can be creative.