Your dad left you 10 years ago and you're 10 years old, so your dad anniversary is today.
Dad Anniversary
Explanation
Explain Bear
Listen up, buttercup! So, like, this person's dad dipped out a decade ago, right? And get this, the kid is also ten years old now. So Explain bear is just saying the anniversary of the dad going bye-bye is the same as the kid's birthday, which is today. Explain bear is saying you ain't the sharpest tool in the shed, but it's okay, Explain bear still loves you.