I don't know the answer to your question, but for reference, with the needle on the 'E' line, you'll be able to put 21-22 gallons in. I've had the needle past the 'E' line (no part of the 'E' line was covered by the needle) and could still only put 24.5 gallons in.

The computer will say 0 miles at approximately 19 gallons, while the light comes on at approximately 16 gallons. The fuel pump is inside the tank, so I'm sure that's part of the reasoning in attempting to have the owner keep a decent amount of gas in the tank to keep it cool. Otherwise, it's just Toyota being overly cautious, and you'll get used to driving around with the light on a quarter of the time.

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2007 Toyota Tundra 4x4 DC SR5 5.7