737 Spoiler deflection

Hello,

I've found several sources suggesting that the 737's flight spoilers (without Short Field Package) can move to a maximum of 33/38 degrees, and the ground spoilers to 52/60 degrees.

However, my question, since I've been unable to find an answer, is what determines at which deflection the spoilers actually will deploy at? I'm wondering since there's not a hard and fixed value, but instead, a span between 33 to 38 degrees, and 52 and 60 degrees.

Thanks.