How n why is it that m spike is below 1 but plasma cells are 15 percent in the bone marrow pls kindly explain?

Immunohistology: Normal plasma cells in your bone marrow would not cause a high M spike. Rarely, abnormal plasma cells do not cause an M-spike. Causes of reactive bone marrow plasmacytosis include infection, malignancy, inflammation, Castleman’s disease, anemia, diabetes mellitus, cirrhosis. In most cases the plasma cell infiltrate is less than 20%, The cytoplasmic light chain ratio differentiates MUGUS