winisd says what?

just an fyi, im an amateur DIYer here. so, i just go a Boss 2 loud 12 inch sub for a friend. i think the number is ava-129c... well, i found the thiele/small specs and put them in the WinISD program to design the box. I stumbled across something that just doesnt seem right to me. the sub is 600 watt max and 96 spl efficiency. is it possible to hit close to 130 db with a ported box of 8 cu ft at 35hz tuning with that sub? it seems not that reasonable to me, but im only a beginner, so what do i know. i've done a fair amount of boxes, yet this still seems strange. of course, i've usually worked with less efficient drivers...Oh, did you say something? sry, the air was vibrating too much.

8 cu ft is quite a large box for two 12's I'm skeptical of those specs also because a 96 db at 1 watt rating is too good for a crappy sub