With 10 hours you can pretty much go anywhere in HK. However, assuming you want to stay reasonably close to the airport the question is how far do you want to run?

Before departure: download the CityBus app and on google maps download Lantau area into the offline memory. I'd also suggest the "all trails" app.
When you arrive go to the vending machine next to the airport express desk and get a octopus card with credit on it. (this will be about 20 USD payable on a card. 5 USD is a deposit and 15 usable. when you leave it is refundable from a service desk).
Buy water, lots of water. I met some Americans on Lions Rock trail the other week who had no water as they hadn't realised how hot it would be. I had to give them a couple of ltrs of mine. The rescue resources in HKG are fab but you really don't want to have to use them. Speaking of which: In the event of an emergency on a trail the local emergency number is 999. The air quality can be an issue.

Very close to the airport :
Get the bus (or jog) to the Fuel Tank Farm. Then run the perimeter road to the Aircraft Maintenance Area. It's a flat out and back following the coast and new bridge. It's soulless but if you like aeroplanes and busses you'll see plenty go past. Big advantage is it can be as short or long as you want (from under 5k to about 10 if you go the whole way) and you will meet plenty of staff doing the same run and can bail out onto a bus at pretty much any point should it be too hot. You can add in the steps to the airport lookout hill (the view is so-so).

Next step up Get the bus to the yat-tung estate then follow the coast to the village of Tai-O. It's coastal, so mainly flat but with some very short steep sections. It's about 16km ish one way and I tend to do it as a mixed walk / run. You can then get the ferry back to Tung Chung (can pay with octopus) and the bus back to the airport.

Next level again: follow the basic route as above but instead of going to Tai-o turn up the Nong-Ping 360 escape path. It's steep , mainly stairs and paved / boardwalk. It can be slippy in damp weather. The view is fab in decent visibility. About 7-8 Km (depending on exactly where you start) . Then at the top go see the Big Buddha, take tea, buy chintzy souvenirs and take either the cable car down (pricy) or the bus (cheap but longer).

Finally I'd start in Tung Chung and run / hike to Discovery Bay. it's about 6.5 km over a hill, quite steep in places but ends in the plaza of DB a slightly unusual community. If you're uber fit and not too sweaty you could then take the ferry from DB to Central HKG which will give a great view of the city and the express from central back to the airport. Allow about 5 hours for the whole thing.

If you're prepared to explore further then things like the Dragon's Back on HKG island become viable.

Enjoy, it's an amazing place.