In Altium Designer, the L, M, N designators refer to the pad and footprint size.

• Least is 10% smaller than N; use for a really tight corner
• N is Nominal size
• Most is 10% larger than N; relaxed, good for hand assembly

All are compliant with the package size, so you can use any of them when laying out and the component will still fit.

In Altium Designer, the L, M, N designators refer to the pad and footprint size. I believe these are from IPC-7351, but you need to pay for it.

• Least is 10% smaller than N; use for a really tight corner
• N is Nominal size
• Most is 10% larger than N; relaxed, good for hand assembly

All are compliant with the package size, so you can use any of them when laying out and the component will still fit.