It sounds like an exact measurement but i think it's a vague one. If dead center is the center of the tip aimed to the center of the cb, then literally, a one tip english would be exactly one tip's diameter off the center. But I think that is too much, and I think many people refer to a tip's english as very slight, and for ME that would be the side of the tip aimed to dead center on the cb or literally a 1/2 tip. It is illustrated in the first response.
That's just me.
That's just me.