The Sack of Brescia took place on February 18, 1512 during the War of the League of Cambrai. The city of Brescia had revolted against French control, garrisoning itself with Venetian troops. Gaston de Foix, recently arrived to command the French armies in Italy, ordered the city to surrender; when it refused, he attacked it with around 12,000 men. The French attack took place in a pouring rain, through a field of mud; Foix ordered his men to remove their shoes for better traction. The defenders inflicted heavy casualties on the French, but were eventually overrun, suffering 8,000 - 15,000 casualties. The Gascon infantry and landsknechts then proceeded to thoroughly sack the city, massacring thousands of civilians over the next five days. Following this, the city of Bergamo paid some 60,000 ducats to the French to avoid a similar fate.
Question: How many is the difference in the number of casualties the defenders were said to have?
Answer: 7000; 7000