Random seed number. The "random seed" (short for "random number generator initial, or seed, value") determines the set of problems generated. If this is left blank, the computer will pick a random seed for you based on the time of day. If you want to be able to reproduce the exact same set of problems - say, to generate an answer sheet - you must enter a number of your choice as the random seed. Use any number between 1 and 9999. In either case, the worksheet will print the seed number it used at the bottom of the page.
Rows and columns. These boxes are in gray to remind you that by changing these, your worksheet might not fit correctly on a single sheet of paper. The default values make a worksheet that will correctly render onto one US letter-sized page with sufficient room for answers to be written in.
Use dash as the subtraction symbol. Some browsers cannot display the special subtraction symbol; if your browser cannot display it, check the "Use dash" box above and the dash character will be used in the table instead of the special character. Test: you should see a small subtraction symbol inside these quotation marks: "–" (compare to the dash character "-").
Use X as the multiplication symbol. Some browsers cannot display the special multiplication symbol; if your browser cannot display it, check the "Use X" box above and the letter X will be used in the table instead of the special character. Test: you should see a small multiplication symbol inside these quotation marks: "×" (compare to the x character "x").