there's even a secret -17!`name that will show the details. e.g.

  //100k random 32b ints ... 
  l>v:100000?255
  l>v
  196 124 18 216 63 169 151 173 126 99 90 133 92 158 217 169 201 191 138 105 13..
  // but actually they are 1/4 the size e.g. int8
  l>-17!`v
  1b        // is compressed?
  100032j   // compressed bytes
  400000j   // original bytes