Reduplication of the noun 小时 in 走了半个多小时小时 Chinese uses reduplication of verbs and adjectives all the time, but I can't find any explanation of reduplication of nouns to explain 小时小时 in this sentence:

(from a Mandarin Companion reader, 地心游记, chapter 5. Our heroes are out of water...)


  不管怎么样，我到水就好。我们一起跟着老许去找水，走了半个多小时小时，我们听到了地下河水的声音。


I interpret 半个多小时 as "more than half an hour" (but less than an hour).  What does the repetition of 小时 mean here?
It is a typo. We never use reduplication of noun 小时.

There is another typo in this sentence. 我到水就好 should be 找到水就好.