SHM soap bubble

How did they get the underlined ‘2’ factor in the solution

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Bro probably bubble is considered to be 2 surfaced so every surface will exert that pressure force imo

But we have already calculated the net overall excess pressure as 2*2S/R=4S/R due to the presence of two surfaces isn’t? If we write on individual surfaces, wouldn’t it just be 2*d(2S/r)*4πr² ?