You don't need to know the bottom left axis number. We do have to assume the graph is linear, and not some kind of negative exponent log graph. But given the rest of the content, I think that is safe to assume.
Any company that experiences significantly more growth than they were planning for will have capacity issues.
The priorities are most inline with that. The are way beyond the point that they can just add more hardware. They need to make the backend more efficient, and all the stated goals are about helping there.