Hi Jan. As Sue stated. Plus this information.
This is from the NovoNordisk website here in the UK.
3. How to use NovoMix® 30
Eat a meal or snack containing carbohydrates
within 10 minutes of the injection. NovoMix 30
may also be given soon after the meal.
It would be best to have it after your meal as you may not get your meal within the 10 minute time frame.
Ken.