Estimate line quantity

I'm working on SuiteTalk c# soap application.

When i'm creating estimate from soap request, i cant add estimate line with quantity > 1.

estimate.itemList = new EstimateItemList

            {

                item = list.Select(i => new EstimateItem

                {

                    item = new RecordRef {internalId = i.ProductId.ToString(), type = RecordType.lotNumberedInventoryItem, typeSpecified = true},

                    quantity = i.Quantity, //2

                    rate =  i.Price.ToString(),

                    amount = (double) i.Total,

                    description = i.Description,

                    price = new RecordRef{internalId = "-1"},

                }).ToArray()

            };

When i save estimate and look at it in UI, there is only 1 item in line

Also, when i'm trying to create quote with item, that have 0 Available - i'm getting error, but i can create quote with this item in UI. How can i allow to create quote with items, that have 0 Available?