Looking at the example on the left, you look at the active cell (surrounded by the bold lines) and find number which is the product of two different numbers in the cell. In this case, you would click on '96' which is the product of 8 and 12. Once you get the correct answer, a new cell is highlighted. Once you complete all those cells, a final puzzle is presented using the answers from those cells. Upon successful completion you are given a final score based on the time it took you to solve plus any penalties you may have accrued for incorrect responses.
If you want to make this competitive in your classroom, you could post leaderboards for the day or week with the top scores of the week. If you choose to do this, you could go "old school" and write names on the board or go digital using Google forms. Tammy Worcester provides a tutorial on setting up a Google forms to create these leaderboards here.
In the SAMR model of evaluating technology integration, this is clearly on the lower end ... augmentation at best. But it certainly provides a fun alternative to standard worksheets. It is far more than just 6-7 problems; students are likely doing dozens of calculations as they try to determine what set of numbers works in each cell.