Definition of that adverb from the Oxford Advanced American Dictionary

     

    that

     adverb
    adverb
    NAmE//ðæt//
     
     
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  1. 1used when saying how much or showing how long, big, etc. something is with your hands I can't walk that far (= as far as that). It's about that long.
  2. 2 not (all) that not very, or not as much as has been said It isn't all that cold. There aren't that many people here.
See the Oxford Advanced Learner's Dictionary entry: that