Geesus Shrags, 10 days off in 28? Sounds too good to be true doesn't it?
Are they 10 days in your home port? Do they include "normal" hours off, ie, night or normal sleeping hours? Are there any weekends involved? Are any of them consecutive days off? For christ's sake, don't be blinded by what seems a "reasonable" offer which then precludes you from having any semblance of a "normal" life!