Does an effect that gives a creature a new base power and toughness override counters on that creature in the layer system?

In Magic's layer system, continuous effects that modify power and toughness are applied in a specific sublayer order within Layer 7. Effects that set a creature's base power and toughness — such as Humility or a card like Mysterious Egg becoming a 0/0 and then getting counters — are applied in Layer 7b, while +1/+1 and -1/-1 counters are applied in Layer 7c.

Because Layer 7c comes after Layer 7b, counters are always added on top of whatever base power and toughness was established in 7b. A base P/T effect does not erase or override counters; it simply sets the starting value before counters are counted (CR 613.3c, 613.3d).

For example: you have a Grizzly Bears (2/2) with two +1/+1 counters on it (making it effectively 4/4). If an effect makes its base power and toughness 1/1 (Layer 7b), the counters are still applied in Layer 7c, so the creature ends up as a 3/3, not a 1/1.

This means players can never use a base P/T replacement to "zero out" counters on a creature — the counters persist and are added after the base value is set. The only way to remove counter effects is to actually remove the counters themselves.

Note: Other modifiers like Anthem effects (+1/+1 to all creatures) sit in Layer 7d and are applied even later, so the full order for a creature is: 7b (base) → 7c (counters) → 7d (other effects).