How unusual is this maths ability in a 3 year old

[WhyNotMe40]

And what should I do about it (if anything)?
So I knew he could count well - not just reciting numbers but accurately count objects up to about 40 - after which he gets bored.
But we've recently discovered her can do simple sums in his head. He could work out simple addition of single digit numbers with barely a seconds hesitation. He has also replicated this at the childminder's so it's not us subconsciously prompting somehow.
The childminder has also discovered he can say how many tens in twenty, thirty, forty etc.
I don't have much experience with small children but it seems unusual to me. I certainly haven't done any maths work with him or even mathematical games - just the usual Lego, play dough, etc
If I encourage this will it upset his reception teachers in September? Or should I find some maths games? He has always loved numbers and shapes and patterns, but I just thought he could count and that was it!
Any advice?

My eldest could do this, the younger two, not a chance.

Ah yes baking. He loves baking....
I've put on 1.5 stone!

Very unusual, don't encourage or discourage, sounds like maths is his 'thing' so let his skills just evolve naturally.
Some great fine motor activities are play dough, using tweezers to pick up coloured pom poms or bits of pasta etc
At school we often play a simple game where each child takes it in turn to scrunch up scrap paper and throw it into the 'goal' They love it and it's great for building up those important muscles for writing etc

Whoever suggested dot to dot - thanks! He's absolutely loving them and has raced through all the ones we have - need to go and get him his own book 😀
He's also picking up letter sounds and blending really quickly. I think maybe I've been underestimating him and he's been bored?

My 3 year old is ahead for numeracy according to nursery but is no where near your son. She can confidently count to 30 but sometimes forgets 15 and she can do single digit addition and subtraction. She is also doing 50-100 piece puzzles with some help but goes in phases as to whether she can be bothered or not. However, she’s more of an all rounder and seems to progress in something and then stop to do something else. She hasn’t really done anything new that’s mathsy for 6 months so I suspect in a few months time she’ll do something new again. She was the same with literacy stuff. She seemed to be on the brink of wanting to learn to read and then lost interest to focus on something else.

I’d maybe try and give it a pause and do something else with him that he doesn’t find as easy naturally, particularly social type stuff. My nephew was amazing at maths: I’ll be amazed if he doesn’t study it at university but he was bored shitless at primary school. He was doing the countdown maths puzzles in his head when he was little and was beating all the adults around him and still has a freakish brain for mental arithmetic. As much as teachers say they differentiate, I’m not convinced it always works when you’ve got a child with a skill that’s so far ahead.

I thinks he is very strong in maths. I would buy a few maths books for year 1 and gently introduce some of the concepts. I would also buy some maths games such as fraction pizzas, 100 square board and start playing with coins.