Time for Twitter's Q3 Earnings. Here's the Key Number to Watch.

Revenue growth? Sure. Profits? Nice to have.

But there’s one thing investors will focus on when Twitter reports its Q3 numbers this afternoon: Users, and how many of them the company added in the last three months.

After spending the first half of the year with its stock under a cloud, Twitter surprised Wall Street three months ago with its Q2 user numbers. Its shares have been on a tear since then. Now we get to see if Dick Costolo and company will keep it going.

Twitter ended Q2 with 271 million monthly active users, and RBC analyst Mark Mahaney thinks investors are looking for something between 278 million and 284 million today. If they hit 280 million users, that would be a 21 percent increase over the previous year. Last quarter, monthly users grew 24 percent.

It’s worth noting, by the way, that Twitter posted very similar growth numbers in its Q1 report, which Wall Street didn’t like at all. Expectations!

Playing the higher-lower game with Wall Street is a pretty silly way to spend time, but it’s a fact of life for Twitter now. And analysts do have a point when they fixate on user growth.

Twitter’s ad numbers are impressive for a company its age — it’s going to do more than a billion dollars this year, and a few years ago it had no ad business at all — but lots of advertisers are still experimenting with Twitter, not committed to it. Commitment won’t happen until they’re convinced they can easily reach lots of people, and to do that Twitter still needs to bulk up.

But you shouldn’t expect to hear any more from Twitter about new metrics designed to show that its real user base is much larger than reported. Twitter has previously discussed rolling out numbers that highlight how many “logged out” users it has — people who see Tweets and or visit Twitter.com but aren’t signed into the service — and some people thought they might show up last quarter. They didn’t do that.

People familiar with the company say they won’t be coming out today, either.

There are at least two good reasons for that: For starters, Twitter seems to be doing okay without those numbers. And more practically, Costolo has already said that Twitter isn’t really trying to generate revenue from those logged-out users, for now.

Once you see that change — one sign might be more experiences like the one it created for casual users during the World Cup — you might start hearing about alternative metrics again.

For now, here’s Mahaney’s useful cheat sheet for today’s numbers. You can click on the chart to enlarge it.

This article originally appeared on Recode.net.

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