First player moves at least the min number of units based on operations range, but not more than max; then second player do the same; than first player do the same again (if has units not ordered yet) and so on.
This interpretation is correct. Then if one player has run out of units, the other player 'Uses' his remaining Unused units.
So let's say we both have an Ops Range of 3-6, and you have 4 units left and I have 11 units left. You 'Use' three units and then it is my turn. I choose to 'Use' four units. You 'Use' your remaining unit, and now you have no more. I can now 'Use' my remaining seven units, even though seven is larger than my Ops Range.