Tire tube

[gdog]

Have a tubless tire that has a crak in it so i bought a tire tube for it and my tire is 20 x 8 x 8 and the tire tube is 20 x 8 x 7 the guy at tractor supply told me it would fit my tire i got home put it in the tire and started filling it and in the prosses of puting it in i put a hole in the tube so im going to get this sealer stuff i say at vip it like fix s flat but suposivley better so any way my questionnis is the tube the right size