Will having a protein shake at 9:30am pull me out of IF fat burning mode?

Shake Serving:

Whey Protein
Energy 435kJ / 103kcal
Fat 1.9g
Carb 1.0g
Protein 21g

Last meal by 8pm, first meal at 12:30am

I have read that as a general rule of thumb if you drink something with fewer than 50 calories you are still in “fasting mode”. Anyopne confirm this? MM says it in his book IIRC.

If you look at the calorie counts on the shake, they are low, energy is round 100 kcalories, this is more comparable with a cup of tea with milk than a meal.

Does taking in this amount of energy end your fast? Where is the cut-off if so? 50 cals? 75 cals? If I take it in 2 halves an hour apart will this allow IF to continue?

Basically, I want to titrate my protein shake to fit in and see if it works.