Write the calculation, then find the (rounded) estimated number that matches. Finally, find the answer the matches the estimation.
The first watch has been done for you.
Check to see what the numbers have been rounded to, some are to the nearest 10 (like watch 1), some are to the nearest 100 and others to the nearest 1000.
Set your work out like this:
Watch number 1
Day 1 + Day 2
3452 + 2505
3450 + 2510 = 5960