Small correction, the magic number is 10 Toronto is still in the 4 slot. 163 - 80 Sox wins - 73 Blue Jay losses = 10. Same math applies to Texas, who also are at 73 losses.
Sox do not hold the tiebreaker over Toronto as the Jays took the season series 9-4. They have 3 left with the Rangers; Sox took 2 of 3 earlier this year.
To get the magic number, you start with 163, not 162. If you use 162, two teams that have the same record would both get their magic number to 0 vs each other but neither would have clinched a playoff slot (I’m not getting into tiebreakers). In theory, one would need 1 more win (a winner take all playoff game in the old days