Min. lot arr. unit

This is the minimum quantity of unit with which the MRP engine issues the subcontract orders.
The MRP engine will not issue the subcontract orders with the quantity less than the quantity set here. (In other words, quantity of the subcontract order will be rounded up to have at least the quantity set here.)
This parameter is useful in the scenario where the minimum order quantity is fixed. For example when the minimum order unit of the item A is set to 100, [Min. lot arr. unit] of the item A should be set 100.
This is the quantity per Supply Unit (Please note that this is different from the [Qty. per unit])

Difference between the [Min. lot arr. unit] and the [Lot arr. unit].
The [Min. lot arr. unit] is the minimum quantity of items required to place one order. On the other hand, the [Lot arr. unit] is an order increment unit. For example, if the [Min. lot arr. unit] is set 50, and the [Lot arr. unit] is set 10, the possible quantity of orders are 50, 60, 70...).