code: function (iCurrent) {
  			// deduct indices reserved from current z-index
  			var iMaxZIndex = iCurrent - Z_INDICES_RESERVED;
  			// initial minimum z-index
  			var iMinZIndex = iCurrent - Z_INDEX_STEP;
  			var iNextZIndex = fnGetLastZIndex(iMinZIndex, iMaxZIndex, aAssignedZIndices);
  			aAssignedZIndices.push(iNextZIndex);
  			return iNextZIndex;
  		}
docs: Returns the next minimum possible z-index based on the passed z-index value.
  @param {int} iCurrent Current z-index value
  @returns {int} The next minimum z-index value
  @private