Your colleague is either kidding you, or he or she is a superwriter from another planet. Frankly, I don’t know of anyone of my acquaintance who can dash off 30 words per minute on a word processor or typewriter, for that speed means one word every 2 seconds without letup. Another thing: What kind of writing does your colleague do anyway—news story, feature article, essay, or what? It seems to me that any human who can compose 300 words into an intelligible exposition in 10 or 15 minutes, particularly an article that uses multi-syllable words like “infinitesimal” and “extraterrestrial” every 10 words or so, is simply out of this world.
As to the “50/10 suggestion” of your two colleagues—50 minutes of writing and 10 minutes of rest—don’t fret if it doesn’t work for you. It sounds like outrageous nonsense to me. I don’t think it will work for 99.99% of the entire writer population of this planet. In short, Miss Mae, I suspect that those two colleagues of yours are just pulling your leg.