Understanding Tube Test Results

I've owned a vacuum tube based pre for about six months and am ready to start experimenting with different 12au7 and 12ax7 tubes.

If a seller refers to test results in the following format:
Tube 1 3000/3000
Tube 2 3100/3200
Min = 1800
What does it mean? (The numbers are made up for sake of the example)
I've searched all over and couldn't find an explanation. Thanks in advance for your input.
The minimum good reading for these tubes on this tester is 1800, these days minimum good is considered 65% of the average score for a new tube which in this case would be 2800.

Each tube has two triodes so there are two scores for each tube. These tubes test above average new, so they are probably new or lightly used.

Also the difference between the highest and lowest scoring triodes is 200 points or about a 7% difference, so these would be considered a matched pair but not closely matched.

There are all kinds of testers and they give their readings in a variety of numbers, so you can see these same tubes scored as 90/90, 91/92 for example.

Some testers are more accurate than others and tube testing is an art not a science. It takes some practice to get a tube to give the same reading twice.

You can google Hickok, a maker of tube testers, and probably find more information about testers.

Another option is to buy from a reputable tube dealer. This may cost a little more but you have greater certainty about what you are getting and you have the benefit of the dealer's experience in deciding which tubes would be best for you. Do a search for tube dealers and you should get some names.
great answer. Only one thing to add; if you are paying any kind of a premium for test results on tubes you should find out when the tester was calibrated.