That is not something new, the 'silo_reset_level' parameter belongs to the silo level plugin and is used with 'silo_reset_time' to calculate 'silo_level', and to plot the graph. 'magazine_content' belongs to the 'scottecom' plugin, and its value comes from the corresponding data in the burner control box.
Previously the silo level plugin didn't provide any numerical value for the remaining level, it only plotted the graph, so the only place to get a value to put on the system image was to read from 'magazine_content'. Now that there is a 'silo_level' parameter calculated by the silo_level plugin I replaced 'magazine_content' in the default system image with this 'silo_level' (which you can change back if you like), but that doesn't mean 'magazine_content' is automatically set, it just mean that you can ignore it if you want to.
(Or you could use the 'calculate' plugin to make a small script to automatically set magazine_content with the value from silo_reset_level whenever silo_reset_time changes, everything is possible...)