What is this condition?

Wound area $A(t) = A_0 r^t$, where $A_0$ is initial area, $r$ is daily decay factor, $t$ in days. Heals when $A(t) < 1$ cm².

From image, estimate $A_0 = 16$ cm², halves every 3 days so $r^{3} = 0.5$, $r = 0.5^{1/3} \approx 0.7937$.

$$A(t) = 16 \left(0.5\right)^{t/3}$$

$$1 = 16 \left(0.5\right)^{t/3}$$ $$\left(0.5\right)^{t/3} = \frac{1}{16} = \left(0.5\right)^4$$ $$\frac{t}{3} = 4$$ $$t = 12$$

At $t=12$ days it reaches 1 cm², so heals after 12 days.

12