It makes sense that you would place the amount of powder in the feed chamber that corresponds to the z-height of the object to print plus a bit more as a buffer. The printer should cease to load the build chamber when the print data end is reached. Any excess powder that is placed in the feed chamber will be subject to heating, reducing its value. I have not examined the software for this aspect, but if it is not of this nature, it is unquestionably wasteful.