If the total worth of your AAA players, plus the salary of your roster, puts you at $90,000,001, then you will be placed in the 100M TOC. An 80M TOC includes teams with total roster value of $70,000,001 - $80,000,000. A 90M TOC includes teams with total roster value of $80,000,001 - $90,000,000. Etc.
It's not perfect, but what do you want them to do? Have TOCs in brackets of $1,000,000? Those would never fill.
And in almost all cases it's more realistic (and fair) to bucket your team in with a $100,000,000 team than one with $80,000,000 total roster value.