Why two numbers
Word counters disagree with each other more than you would expect. A hyphenated compound is one word to some and two to others, and the same goes for a dash typed without spaces around it. For most drafts the difference is irrelevant. At 646 words it is not.
So this shows the spread instead of pretending there is one authoritative answer. If the two numbers straddle 650, paste the draft into the real Common App field before you decide anything. That field is the only count that actually matters, and it is better to learn this in September than on deadline night.
Being under the limit is fine
The 650 is a ceiling, not a target, and treating it as a target is how essays get padded with a paragraph of setup nobody needed. The far more common problem is an essay that hits 649 and still has not said anything only its writer could say.
That said, well under 500 usually means the story has not been developed yet rather than that you found a leaner way to tell it. If you are at 380 and out of things to say, the missing material is almost always the part after the moment: what you decided, and what you did differently afterwards.
Common questions
What is the Common App essay word limit?+
The Common App personal essay field accepts 250 to 650 words. The field enforces both limits.
Does the Common App count words the same way my document does?+
Not always. Word processors disagree about hyphenated compounds, dashes without spaces, and numbers, so a draft can read 648 in one place and 652 in another. If you are within a few words of the limit, paste into the actual Common App field early and trust that count.
Is it bad if my essay is under 650 words?+
No. Any response from 250 through 650 words is accepted. The useful question is whether the essay has enough evidence and reflection, not whether it reaches the maximum.
Is my essay stored or uploaded anywhere?+
No. The counting happens entirely in your browser. Nothing is sent to a server, saved, or logged.