What do low absolute monocytes meam?

Various reasons: A low monocyte count can occur for a variety of reasons: physical illness, medications, or vitamin deficiencies. Illnesses that affect the bone marrow, such as hiv, rheumatoid arthritis, or lupus, are among the most common causes for a low monocyte count. This symptom may also develop as a side effect of some medications or deficiencies in vitamins such as folate (folic acid) and vitamin B12 deficiency.

Usually nothing: Reference ranges are set so that 5% of healthy people randomly fall outside. If your absolute monocyte count is a bit low, and you feel well, and everything else is reasonably close to normal, i would ignore it. If monocytes are absent, i would think first of a lab error.