The company cites two revenue numbers in its second-quarter financial results, which came in above analysts’ expectations. One expresses total sales ($64.5 million for the quarter ended June 30, up 70% year-over-year). Another reflects “base” revenue ($56.4 million, up 84%) outside of approximately 10 customers that haven’t made 12-month minimum revenue commitments to the software company.

That handful of accounts represents an important, but variable revenue stream. That’s why Twilio describes the base number as “one of the more reliable indicators of future revenue trends.” Expect the company to talk up both measures in the future.

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Twilio ended the quarter with 30,780 active customer accounts, compared with 21,225 a year ago.

One of the company’s variable customers is messaging service WhatsApp, which was called out as a risk consideration in Twilio’s IPO prospectus. Other big customers it cites publicly include Uber (UBER), which uses the software to send texts between passengers and drivers. More recently, Twilio entered into relationships with Facebook (for Messenger) and Salesforce. Both have built Twilio communications technology into their own cloud services.

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Looking forward, Twilio anticipates total revenue between $63 and $65 million in the third quarter ending Sept. 30. Of that amount, it projects that $58.5-$59.5 million will come from base accounts.

Line Just Had the Largest IPO in 2016 [fortune-brightcove videoid=5035631645001]

Twilio made its highly anticipated trading debut on June 23 as the first tech “unicorn” (companies valued privately at more than $1 billion) to go public in 2016. Its stock closed Monday at $42.50, almost triple that price. Twilio shares gained another 2.43% in after-hours trading, after its positive earnings report.