A new fast food restaurant opened 5 months ago. The table belows shows the number of burgers they've sold so far.
Month | Burgers Sold |
1 | 2,075 |
2 | 1,985 |
3 | 1,279 |
4 | 3,583 |
5 | 3,488 |
| 12,410 |
The next month (after spending some money on an ad) they sold 6 times as many as they had sold in the previous 5 months. How many fewer burgers did they sell before running the ad than they did after running it?