How to handle this for next time

It’s likely that you miscalculated the carbs for your meal.
The pump may have been unable to stabilise your level from 18.4+ on its own even with 5.7 units IOB.
If it works the same as my earlier M670g the pump could be set to sound an alarm say at 10. Well before you reached 18.4. This would prompt you to take additional bolus if necessary, but be careful not to overcompensate.
Regular monitoring of your screen (if you’re not the car driver!) will help.
Another possibility is that if it’s a new cannula it might not be working properly (yet).

Hi @Jess1D

Agree with Dexta - also there could be other factors at play too, such as possible stress levels causing a bit of resistance, I find if I am eating out with people I haven't seen in a while, a bit of stress/excitement could hit my control too, but most important of all, it is a one off, if it's a repeated event then a bit more vigilance in regards to pre-bolus would help the situation so don't beat yourself up too badly on this.