Can someone give me an explanation of soft_end_stop_min and max.

Can someone give me an explanation of soft_end_stop_min and max. I noticed on a the rostock_max the settings are

soft_end_stop_min_x = -0.05
soft_end_stop_min_y = -0.05
soft_end_stop_min_z = -0.001

soft_end_stop_max_x = 0.05
soft_end_stop_max_y = 0.05
soft_end_stop_max_z = 0.6

how are those numbers figured out? Are the negative min values there because of the hardware endstops? how is max measured in relation? how does Z fit into the picture?

I think this might be keeping me from having a leveled print bed, as my printable area on my printer is 254x254mm by 304mm tall. My settings are

soft_end_stop_min_x = -0.128
soft_end_stop_min_y = -0.128
soft_end_stop_min_z = -0.001
soft_end_stop_max_x = 0.128
soft_end_stop_max_y = 0.128
soft_end_stop_max_z = 0.340

which seems incorrect to me.

Thanks,
Jim