BS17-075 Strangle Fog

please help here abit, i dont understand part sof the text:

(Flash Step) Move 1 core from an opposing spirit to your opponent's reserve. If your opponent has three or more total core than you, from their life, field, reserve and trash, send 3 more core from an opposing spirit to the void.

thnx in advance:-)

update: could anybody pleaseplease help with this:-)

thnx you in advance.

I got cores has 20 cores.
you got 15 cores.

This magic played by you.
moved 1 core from my spirit.
I got more cores than you(5 cores).
My 3 cores move to Void.

results:
I got 17 cores.
you got 15 cores.

Did i answered?
effect translate[my version]:
Move 1 core from opponent's spirit. Total up both players core, if opponent's core is 3 cores(or more) more than me, i can move opponent's 3 cores to void.

yes thnc, almost ok, but little detail remains unclear please:

why are are cores in trash also counted?! they do not give any advantage in that situation?! ("and trash")