Think about it this way: 9 * 10m = $90 million. But probably they couldn't have sold the whole 10M slug at 24. Let's guess and say they left more like $45M on the table.

They are currently at a ~2B valuation.

45M / 2B = 2.25%

Twilio is (in theory) a high growth tech company. Say they want to grow at 15% a year. 2.25% / 15% = .15 or about 2 months worth of growth.

2 months is certainly something, but in the grand scheme of things isn't the hugest deal in the world.