Binge worse than expected. Me, or the carb count, or?

So yesterday was a good day up until 11pm.
I'd had a spoonful of yoghurt in the morning then a large frittata and salad meal at lunch time, for a day's total of 12g carbs
Then at 11pm, I had 1 square of a new Waitrose75% dark chocolate with ginger and turmeric BUT I didn't leave the bar in the cupboard and the next thing I knew I had eaten 6 squares (it was lovely). According to the packaging it is 38g per 100g so I had eaten 22.8g of carbs, late at night 11 hours after any other food. BUT still only a daily total of 34.8g
Feeling guilty I tested bg after an hour 10.5, not good, but hoping for a quick spike, stayed awake for another hour and it was 10.5 still!. A quick hand wash and testing the other hand was 9.5!
Went to bed , slept badly with guilt and getting very hot. Waking bg was 5.9, phew!

But I don't understand the large, sudden and prolonged spike. I have been trying OMAD and don't normally spike for 15-20g carbs in one sitting, so what was going on here? I've tested for 2 squares of chocolate before and had not had such a reaction

I'm wondering if the carb on the packaging is wrong as it seems low for the amount of sugar (7% of it was added crystallised ginger).

Thoughts?

EllieM said:

Maybe acquire a taste for Lindt 95% chocolate - 7.5g for an 80g bar and it's hard to eat more than 2 squares at a time (10 squares per bar). I've binged on 4 squares but I really don't think you'd be able to manage a whole bar....

(And no, that is not a challenge)

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Yep, thats my normal treat. This one was way too easy. I just don't understand why it caused such a spike