I have a rbc of 5.51 this year which is up from 5.34 last year what does that mean?

Nothing: It's fine. There is always a little variability from one sample to another, depending on hydration status, etc. One rarely gets the EXACT same test result from one sample to the next.

Not that much: That difference in a spot blood test is not really a difference. The key is to look at the Hemoglobin and Hematocrit levels too. If they are above the normal ranges, then Polycythemia is the issue. This can cause blood to have a thicker viscosity and therefore clot up together easier. Different causes for this. COPD is probably the most common in our society.

Minor fluctuations: This minor fluctuation in your RBC is of no clinical significance. Keep regular appointments with your dr. for routine care. Best wishes.