Basically just put your offers all the way left and submit (0 bonus and min contract).
Take the number they give, add about 30-35k to that. Enter that number into the bonus section and it'll move the bonus to 75%. If the number in the bonus box is not exceeding the given number after that, take the salary and move it right slightly until it reaches that number or right over. Then offer that. you don't really need the excel sheet in my opinion.