there are three timing marks
1 is on the cam sprocket this lines up with the corresponding mark on the piece of plastic behind the cam sprocket. the cam sprocket will be stamped with the letters t c with a cut out between them line this cut out up with the arrow.
the second one is on the crank pulley at the bottom, it is stamped again and lines up with the arrow on the piece of plastic behind it
the third one is on the distributor body, line this mark up with the rotor arm by rotating the distributor body in the block.
if all three are lined up and the belt fitted correctly then it should be ok
this is what we did when golfvr6 did my cam.