You should ask the college admissions office to be sure, but it sounds to me like this:
for example if they want two subject tests, one science & one math, and you took 3 subject tests (Chem, Physics, Math 1) twice, and you decide to submit your Chem & Math scores, you should submit all Chem & Math scores and not submit Physics at all (because irrelevant to application).
Unless you did really well on all your Subject tests then you might as well submit them all.