If you have a Labcorp results report you should probably have the two following lines from a CD57 test:
%CD8-/CD57+ Lymphs -% 2-17 (normal range)
Abs.CD8-CD57+ Lymphs -/uL 60-360 (normal range)
The "-" is what your specific numbers are. The bottom number (the Abs (Absolute) number) is generally what is tracked. Under 60 is low. The % number you mention 5% is in the normal range but the other number is often whats referred to in Lyme testing.
Many LLMDs no longer place a significant emphasis on CD-57 - the correlation has still not been firmly established.
Hope this helps.