Just got my answer on the Q&A thread (btw, couldn't find answer before posting my Q despite searching help and forum, though I expect this is discussed somewhere ...)
Tip/ Solution: Adjust floor to bottom of (2nd) object measurement to take into account the height of the first object which you are placing the second object on. Ex: Rug height set at 1/4". Therefore set floor to bottom measurement of table to 1/4". Table can then be placed on top of rug.