The product is correct - there is a LOT of foam in this can.  I have little doubt about the accuracy of its claim to be able to seal and insulate up to 4 windows.  The product is relatively easy to use, but be certain to follow the instructions to "dispense SLOWLY" (their emphasis).  It comes out fast until you get used to the trigger on the applicator tube, and does expand very rapidly.  A very small amount of practice before first use would be helpful.  Also, heed the instructions for proper mixing (shake for a minute, make sure the ball bearing inside is freely moving while shaking).