[Eliot Ness]

The ultimate test is using a tube in circuit, so it sounds like your 47's and doing fine. If you're not sure who tested them I wouldn't worry about the 400 and 1000 Mhos marked on them. While the Knight is a simple emission type tube tester, it sounds like they tested fairly close and in the good range.

The calibration of the Knight 600 is pretty simple and the manual is located here (600tube.pdf):

http://bama.edebris.com/manuals/knight/600tube/

Replace any caps and out of tolerance resistors and the calibration for your simple tester sounds pretty easy.