The different erosion rate estimates have two different types of differences. One is that they were calculated using different isotopes in the rocks (26Al and 10Be). These are slightly different approximations. Unless the sample has been buried (or otherwise violated assumptions of the method), they should be within uncertainty of each other. The second difference is that each one has three reported erosion rates based on assumptions about how production of 26Al and 10Be changes with latitude and altitude. Those reference other publications. St is from Stone 2000: Stone JO. 2000. Air pressure and cosmogenic isotope production. Journal of Geophysical Research-Solid Earth 105: 23753-23759Lm is the same Balco et al., 2008 citation as the calculator. LSDn is from: Lifton, N., Sato, T., Dunai, T., 2014. Scaling in situ cosmogenic nuclide production rates using analytical approximations to atmospheric cosmic-ray fluxes. Earth and Planetary Science Letters 386 149-160