Some lab tests (especially antibody and antigen tests) report results in titers. A titer is a measure of how much the sample can be diluted before the antibodies or antigens can no longer be detected.
A titer of 1 to 8 (1:8) means that antibodies or antigens can still be found when 1 part of the blood sample is diluted by 8 parts of a salt solution (saline), but they can no longer be found at a dilution of 1 to 16 (1:16). A larger second number means there are more antibodies or antigens in the sample. So a titer of 1 to 128 (1:128) means more antibodies or antigens in the sample than a titer of 1 to 32 (1:32).