Caro, Lauri, and Zarb's forest bound conjecture for $f_2$

Let $t$ be a positive integer and let $F$ be a forest. For a graph $G$, let $f_k(G)$ be the minimum cardinality of a set $X$ of vertices of $G$ such that $G-X$ has either $k$ vertices of maximum degree or order less than $k$.

Caro, Lauri, and Zarb's conjecture. If $F$ has order at most

$$\frac{1}{6}\left(t^3+6t^2+17t+12\right),$$

then

$$f_2(F)\leq t.$$

This is a precise conjecture for forests that improves the known general forest bound and was constructed to be tight by matching examples. The paper states that it verifies this conjecture.