My take on the “21st Year” line in Beauty and The Beast

So there’s an element of Beauty and The Beast that, for many years, people have said is a plot hole.

In the opening prologue, the narrator says that the last petal of the enchanted rose will fall on the prince's 21st year. Many people have interpreted this line as being that it meant the petal would fall on the prince's 21st birthday. During the "Be Our Guest" song, Lumiere says that the spell had been going on for 10 years. This has led to people claiming that this meant that the Prince was just 11 years old when the Enchantress turned him into a beast.

Personally, I never thought of it that way. I always thought "21st year" meant that the spell was meant to last for 21 years. Am I the only one who thought this? Even then, there's no way that the prince was 11 when the spell was broken. When Belle goes into the West Wing, she finds a painting of the Beast when he was still a prince. The prince that we see in the painting is clearly a grown man.