It would sound better if they used the usual mathematical description:

'less than or equal to .01' vs 'less than or equal to .06'.

Then the emphasis would be on the 'less than' part rather than on the
'equal' part.  Of course, they could have used the other equivalent
formulation

'not larger than .01' vs. 'not larger than .06'

which means the same thing, but would have sounded scarier.

Although the description for .06 encompasses a greater range of possible
values than the description for .01, it doesn't actually give you any
useful information under the circumstances.  The only real information
is that in either case, the value was below what the test can detect.
In principle, it is more reassumring to know that it is below .01 than
to know it is below .06, but since the test was changed, there is no
reason to believe that there is any change in your status.  Were you
tested with a test with a .01 threshhold, it is extremely likely that
you would still be below .01.