I would ask a dB admin.
You are picking above a certain shipment number for some business reason.
It is not clear if there are multiple items on the same shipment.
And you ignore negative qty although depending on how the table is structured and corrections are handled may not be giving you the expected results.
It might be as simple as creating an inner query without the max date, where an outer query selects the max date for item shipment from the sub query.
Be sure to have a clear business description of what the query is intended to do.
And if the results of this would lead to some other questions, describe those.