Anatomy of that number, just so you'll understand the context:
< is read as "less than", meaning that the result is somewhere below the lowest that the test/equipment used can measure.
0.01 means that the lab is using an ultra-sensitive test. Some labs/doctors only report to 1 digit, as <0.1. There are tests that go to 3 digits out there.
There is no such thing as absolute 0 for a PSA, and the doctors vary in what they report, so we here on the forum consider <0.1 or "undetectable" to qualify for the mythical and mysterious "Zero Club".