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Turns out that the setter had misunderstood the FIFA & IFAB rules and so had thought that in the Football League (including the Premier League), a maximum of 6 substitutes per side could be nominated (which is the default number if no other agreement is made); making 12 per game.
But, as JJ109 and I were aware, the FA has agreed, since 2008, that all its matches may have up to 7 nominated subs per side; making 14 per game.
i.e. it should've been 14 S in a PLFG :)
But I have to admit, I'm still stumped on: 7 BS in TPC (or GB) !!