The compound shown is 1,2,3,4-tetramethylcyclohexane drawn without stereochemistry. Treat the ring as planar and count configurational isomers only (enantiomers counted separately). How many stereoisomers does it have? Give an integer.

The four methyl-bearing carbons are all stereocentres, giving $2^4=16$ up/down patterns. The molecule is symmetric about the C2-C3 bond midpoint, so turning the ring through $180^{\circ }$ about that axis maps the pattern $(a,b,c,d)$ onto $(-d,-c,-b,-a)$; the 4 patterns with $a=-d$ and $b=-c$ are fixed and the other 12 pair up, giving $4+6=10$ distinct compounds. Of these, the patterns with $a=d$ and $b=c$ have a mirror plane and give 2 meso compounds; the other 8 are chiral and form 4 pairs of enantiomers. Total: 10.