The first side with 4000 soldiers is eating 4000*10 = <<4000*10=40000>>40000 pounds of food every day.
Since the other side has 500 soldiers fewer than the first side, there are 4000-500 = <<4000-500=3500>>3500 soldiers on the second side.
Soldiers on the second side are each given 10-2 = <<10-2=8>>8 pounds of food.
The total amount of food the second side eats is 8*3500 = <<8*3500=28000>>28000
Altogether, the two sides eat 28000+40000 = <<28000+40000=68000>>68000 pounds of food every day.
#### 68000