Speedometer off...

I have been looking through threads and getting really confused... a lot of good information but I am now more lost than at the beginning. I have the diagram for the speedo gear for my application and bought a 33 tooth gear but after install I see that at 35 (speed app) the speedo reads 45 so it’s 10 off. Don’t want to keep buying gears so can anyone help me with the math??? Sorry I know there are a lot of threads on this, just wanted help. Thanks in advance guys.