Indicates the maximum number of levels in the ifStack table to be
returned when using the ifStack accounting schema. This object is
ignored if acctngSelectionSubtree is not set to
usdAcctngSelectionSchemaIfStack. When this object is zero, the entire
stack above the starting point(s) given will be returned. When this
object is set to 1, only ifIndexes stacked above the starting point(s)
given will be returned.