Originally documented on the plugin's documentation page in Confluence - probably with better formatting than here.

Also reported on Github here

The current 2.0 version does apparently not work with labels, when used in a free-flow job!

I set up a small test scenario to play with, and it seems like waiting for resources works, but not waiting for Labels.

My tests below:
I used a resource named TEST, with two labels TEST_1 and TEST_2.
Looking at the available resources, it's reported that I have the "TEST" resource, and one instance of the two labels - as expected.
In a free-flow job, I enable This build requires lockable resources, and the tested the following four setups:

Trial 1
Resources = TEST
Number of resources to request = 0
Expectation: The resource TEST and all labels consumed during the test.
On execution:
The test project does not wait for anything.
None of the resources nor labels are reported used.
Note: This might be correct behaviour - provided 0 is used literal, unlike documented in the plugin: "empty value or 0 means all "

Trial 2
Resources = "TEST"
Number of resources to request = 1
Expectation: All labels on the TEST resource will be consumed.
On execution:
The test project does wait for the TEST resource and does consume all Labels.

Trial 3
Lable = "TEST_1"
Number of resources to request = 0
Expectation: The TEST_1 label will be consumed, leaving "TEST_2" available.
On execution:
The test project does not wait for anything.
None of the resources nor labels are reported used.
Note: This might be correct behaviour - provided 0 is used literal, unlike documented in the plugin: "empty value or 0 means all "

Trial 4
Lable = "TEST_1"
Number of resources to request = 1
Expectation: The TEST_1 label will be consumed, leaving "TEST_2" available.
On execution:
The test project does not wait for anything.
None of the resources nor labels are reported used.
Trial 4 is the error I'm really concerned about, as it seems to indicate that only resources can be taken, and not labels.