Sony Vegas Pro 13- greenscreen is a transparent black?

[-Setro-]

what's going on here? I greenscreened in that explosion, why is the background of it a transparent black?
The track for the greenscreen is above the main track.

[Ad Bot]

[ChappersTeddy]

SETRO, WHAT IS THE MEANING OF THIS SUDDENLY VIOLENT AND EXPLOSIVE EDITING? I DEMAND TO KNOW YOUNG MAN

[gebenuwell]

what is happening i am not smart

[-Setro-]

nvm i screwed around with threshold
video is coming soon ;)