Started low carb diet on 6/1. cholesterol test on 8/5 showed: total 256 ldl 196 hdl 40 tri 96 vldl 19 how do i know if my ldl is fluffy or dense?

Need another test: Your question suggests you know that dense LDL is linked to higher risk for future heart disease than "fluffy" LDL. This can be determined through an additional test called particle fractionation, probably adding $150-200 to the lab bill. You have some work to do through diet and exercise to get your total LDL down to 100 if possible. Knowing about "fluffiness" won't add anything at this point.

Probably fluffy: Hi. You would need a more in depth lipid profile to measure whether your LDL is Pattern A (large, buoyant, aka "fluffy") or Pattern B (small, dense). However, small, dense LDL is often associated with triglyceride elevation, which you don't have. But don't be too comforted...that's a very high LDL (with an HDL lower than you'd like) and places you at substantially increased risk! Statin!!!