Janna wrote 400 + 150 = <<400+150=550>>550 words.
Together, they wrote 400 + 550 = <<400+550=950>>950 words.
They have 950 - 20 = <<950-20=930>>930 words left after omitting 20 words.
Then 20 x 2 = <<20*2=40>>40 words were added during the editing.
Overall, they have 930 + 40 = <<930+40=970>>970 words.
Thus, they should add 1000 - 970 = <<1000-970=30>>30 more words.
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