If the TC remains constant, when you're in a + count, you actually are playing through the high cards. It's when the count goes up that you should be worried (if it always was going up, you'd be f***ed).
If the TC stays the same that means the same number of high cards came out as did low cards. You had no advantage. Actually, a slight disadvantage.
I'm talking TC, not RC.
Imagine 5 decks remaining with a +15 RC. The TC is +3. Two decks of play later, if the TC is still +3, then the RC must be +9. Meaning over the course of 2 decks of play, 6 extra high cards came out (HiLo), or an average of 3 per deck.....which you'd expect with a TC of +3.