On the turn if you have exactly 4 outs you need 10.5:1 to call (to see the river). 42 cards you lose, 4 cards you win so the ratio is 42/4 = 10.5:1

On the flop (assuming you have 4 pure outs twice - like a gutshot) then you would need less odds to call the flop (to see the turn) and turn (to see the river). You have your four outs twice so you have more chances to hit (two streets). I usually just count my outs a time and a half (so 6 in the flop gutshot example) as a quick calculation for needed odds on the flop.

The problem Here is that you do not have pure outs. When you give one out to a BD draw you are already accounting for two streets . . . if you then account for it as a whole out twice (on 2 streets) you are doublecounting. Here the estimate of "outs" are not true outs and should not be "counted up". Also, this does not inclue implied odds or reverse implied odds given by the board and the action. Does this make sense?

EDIT: If you PM the chart you have I can tell you where the numbers are coming from. I'm good at math but I suck at the strategy aspect of Poker =)