Impacted versions:
11.0

I don't know if it is an issue, but I think is strange.

`product_qty` is in unit of `product` : https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L240
`reserved_availability` is in unit of `stock.move` : https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L295

`move.product_qty - move.reserved_availability` seems to have no sens, no ?

https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L915
https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L917
https://github.com/odoo/odoo/blob/11.0/addons/stock/models/stock_move.py#L924

thank for your answer

@jco-odoo 
@alnslang 


extra_move_quantity = float_round(
                self.quantity_done - self.product_uom_qty,
                precision_rounding=rounding,
                rounding_method='HALF-UP')
            extra_move_vals = self._prepare_extra_move_vals(extra_move_quantity)
            extra_move = self.copy(default=extra_move_vals)
            if extra_move.picking_id:
                extra_move = extra_move._action_confirm(merge_into=self)
            else:
                extra_move = extra_move._action_confirm()
            # 
            if self.exists() and not self.picking_id:
                for move_line in self.move_line_ids.filtered(lambda ml: ml.qty_done):
                    if float_compare(move_line.qty_done, extra_move_quantity, precision_rounding=rounding) <= 0:
                        # 
                        move_line.move_id = extra_move.id
                        extra_move_quantity -= move_line.qty_done
                    else:
                        # 
                        quantity_split = float_round(
                            move_line.qty_done - extra_move_quantity,
                            precision_rounding=self.product_uom.rounding,
                            rounding_method='UP')
                        move_line.qty_done = quantity_split
                        move_line.copy(default={'move_id': extra_move.id, 'qty_done': extra_move_quantity, 'product_uom_qty': 0})
                        extra_move_quantity -= extra_move_quantity
                    if extra_move_quantity == 0.0:
                        break
        return extra_move
    def _unreserve_initial_demand(self, new_move):