Are those two 10% figures equal only by coincidence?
To me, "boost membership by 10% above trend" means either "increase this year's signups by 10% of what they would otherwise have been" or else "increase this year's signups enough to make membership a year from now 10% higher than it otherwise would have been".
The second of these is equivalent to "membership will be 10% higher a year from now" iff membership would otherwise have been exactly unaltered over the year, which would mean that signups are a negligibly small fraction of current membership.
The first is equivalent to "membership will be 10% higher a year from now" iff m+1.1s = 1.1m where m,s are current membership and baseline signups for the next year, which is true iff m = 11s.
Those are both rather specific conditions, and the first seems pretty unlikely. Did you actually mean either of them, or have I misunderstood?
I am reading the grandparent literally as "increase membership" which does imply that the current trend is flat and the membership numbers are not increasing.
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