Where is 67 ml on a 1ml syringe?

I think you really mean where is 0.67 mL on a 1 mL syringe? If so, and you are measuring Frontline (another assumption), you would be better off to get yourself a Monodose Teaspoon measure from Amazon ($1.50). You would be dosing about 1/8th of a teaspoon for the 0.67mL dose. It isn't exact, but very close and will still do the job.