Hey thanks for your question! The angular clock firmware has a mode you can engage during startup which allows you to fine-tune the needle position for each hour as well as for minutes.
When you open the Arduino Serial Monitor you should see a message that states "Type any key and to enter meter adjustment mode", so you can, for example, type 'asdhf' into the text input box at the top of the Serial Monitor then hit the Send button to engage this mode. You should then be prompted to use the knob to adjust the hours and minutes meter positions to a variety of calibration set points.
In this mode, the needle positions will respond to twisting the knob in either direction. When you have positioned the needle where you want it in response to a prompt, it asks you to type a space into the text input box at the top of the Serial Monitor then hit the Send button in order to advance to the next calibration position.
You only need to perform this procedure once in principle, and the settings are stored and will persist through power cycles. Hopefully this answer is helpful, but please feel free to ask for clarification if I've been unclear in any way.