A:Answer I had the same Q, found out it's a matter of multiple standards for measuring. The method most used in measuring TV/projectors is ANSI. But ANSI measurements can't be used on LASER based projectors for tech reasons {it's complex).
2400 is the "ANSI Equivalent", but the method used by laser manufactures is overall brightness which is 3000. That can be used across other laser units for comparison and is more accurate than ANSI. They're not playing games, it's physics ... :)