The first sign is this wierd saw dust stuff or 'frass' that activates disappointment.
Once cleared away there is a shallow crater with a tiny hole.
Sectioning this apple revealled a similarly shallow cavern. I couldn't find any kind of grub after poking around suggesting these might be Codling Moth 'stings'. That's where the grub starts eating and then stops for some reason and hopefully dies.
So many of the Summer Strawberry apples are affected I lost count!