Price per set (consisting of two items) in description of go

[JadwigaNalepa]

Description of goods:
+ITEM A
+ITEM B
NUMBER OF SETS (PCS): 4
PRICE FOR PCS: 100
TOTAL PRICE: 400
Partial shipments allowed
Two invoices presented no. 1 and no. 2 showing desription of goods:
Invoice no. 1
+ONE ITEM A
PRICE: 60
Invoice no.2
+ONE ITEM B
PRICE: 40
.
Discrepancy stated
+Price per PCS not as description of goods+
Anyone recall an opinion concerning similar situation or might help jugde whether discrepancy is valid