This is a keycap with the number 3 written on it. You can see the keycap on the keyboard
⌨️ or telephone dial pad
☎️. It has a similar meaning to
👌 in the gesture and can be used to represent the number 3, or the third runner in a competition
🥉. Other keycap emojis:
#️⃣*️⃣0️⃣1️⃣2️⃣4️⃣5️⃣6️⃣7️⃣8️⃣9️⃣🔟