Hello @Tillykd and welcome.
Good luck with your new way of eating. Well done on your first successful fast.
This way of eating is very individual and by trial and error we find a way that works for us. Have a look at the huge variety of way discussed on the forum!
The original 5:2 is to have two 500 cal fasts and eat within your TDEE on other days. This would suggest eatingin moderation at your meal out tonight, but don't deprive yourself

If we are hard and set ourselves unrealistic unachievable goals we will fail.
If we are realistic we wil succeed.
Do enjoy your meal tonight and let us know how you get on.