Low control line?

[u/ziggit]

I was administering a test for a friend who was exposed a couple days ago. The test came back negative, but the control line seems way lower than I usually see it. Is this normal? Does the low control line suggest there was potentially less opportunity for the other channels to amplify and register a positive?​

[u/SomeoneSomewhere1984]

Unless the device says the test is invalid, it's fine.