[The sentence is at 1:30 in the video, if anyone else wants to hear it.]
The "at" is really there, and needs to be there. When Jobs says it, it's closer to "eht". Listen for the rhythm in this phrase:
decided at the
Every syllable takes the same amount of time.
de ci ded at the
You might be having trouble with the T sound. Are you making a puff of air at the end? If so, stop doing that. At the end of the word "at", your tongue should still be touching the roof of your mouth. It will sound almost like there's no T at all. This flows naturally into "the", where your tongue starts on the roof of your mouth.
"Decided" is similar, but when there's a vowel after "decided", you end up saying the D at the end. So "decided at" sounds more like "decideh dat". Don't force this -- it's a weak D. When your tongue moves from the roof of your mouth to the bottom, you'll make the D sound automatically.
That's how to say the phrase like a native. If you keep the puffs of air, everyone will still understand you; you'll just be slower.