Double translation is when for example:
Someone translates Spanish into Chinese.
then they would translate the Chinese back into Spanish
The translation of Spanish has to be as close to the exact words used in the first document.
hope this helps
so for example:
I like bananas (english)
私はバナナが好き (japanese)
then in like 1 min later....
私はバナナが好き translate back to "I like bananas"
hope this helps
