I do not know if it is intentional or a bug with manager (cloud) but currently when creating a purchase and you only have one item manager will put the “item name” in the top column instead of using “qty” as the header, when add more than one item it then shows it correctly.
this is because Manager will replace the Qty heading with the UOM of the item when it is the only item in the transaction.
have you created the item under the inventory items tab?
if yes, click edit against the item and check what is entered in the Unit Name field.
the Unit Name is the UOM of the item like numbers, kilograms, etc.
if by mistake you got it confused with the item name, correcting the same would solve your issue.