Bulk Liquor Purchases in Panama Circa 1915

My grandfather's correspondence included an undated receipt for bulk liquor purchases as follows:

• 4 lbs Extract Malaga wine
• 4 lbs Extract Vermouth   
• 2 lbs Essence Rum Punch

The bottom of the receipt had this math: 3.00 + 7.50 = 10.50 + 7.50 = 18.00 - 1.80 = 16.20. This is evidently the cost of the above three items, minus a 10% discount.
The accompanying envelope is the stationery of Peter Ho Syu, PO Box 80, Colon, Rep. De Panama, General dealer in Merchandize, also in Manufacture of Liquors, Wholesale & Retail.

The receipt was for bulk liquor purchases on behalf of Samuel Wertheim, 47 Vesey Street, New York