Did I put plenty fertilizer on my sward? I recently used 'Lawncare' rotary spreader to spread Scotts 29-3-4 Turf Builder....

I recently used 'Lawncare' rotary spreader to spread Scotts 29-3-4 Turf Builder. I don't have Scotts spreader so I go to the store and checked out the opening on Scotts spreader when it is at a 3.5 setting. I tried to match the nouns of the opening to my own spreader at home. I figured that if my spreader's space was the same surrounded by size as the Scott's spreader, then walking at a steady pace should be plenty. I read the package and for my lawn, 3000 sq ft., I should own used 9 lbs, but I don't think I used that much?.Shoud I add more? How would I know if I put too little or too much?
When to verbs up bulbs?
Answers:    Better too little than too much. Weigh out what you involve next time, and check that against what's being spread.

Do you own a calendar of when to fertilize for the grass species you're growing? In much of the US, this is not the best time of year to be fertilizing.
I own this weed plant i.e. more or...
bags of scotts fertilizers have the settings that most spreaders should be set on. you'll know if you put too much if the grass turns washed out and dies.