Why does Iron Spider Costume Have Only 3 Waldoes?

If you look at dr. octopus, he has 2 legs, 2 arms, and 4 mechanical arms which means 8 legs which an octopus should have. In Spiderman red and blue costume, there are no waldoes, but only 2 arms and 2 legs, as we all know, spiders have 8 legs. In the iron spider costume, he has 3 waldoes, or mechanical arms, which means he has 7 legs. 

Since Tony Stark created this for him, I don’t understand why he only gave the costume 3 waldoes instead of 4.
So, how come spiderman in his iron spiderman costume has only 3 waldoes? I have my own reasons.

1.Maybe because of u put another waldo on the back, he would be able to walk correctly. the waldoes can help him walk but if u want it to walk with 4 of them you'd need to put it in the front which would look ridiculous.

2.Maybe Tony Stark made a mistake but by the time he realized it he didn’t feel like fixing it. 

What do you think about it?