I have a very specific question (quite elementary, sorry!)
Let $G$ be a rank $2$ torsion free sheaf on an algebraic surface $X$ (normal maybe?)
Let $L\otimes \mathcal{I}_Z$ be a Gieseker destabilizing subsheaf of $G$ where $Z$ is a $0$ dimensional subscheme.
Is it true that $l(Z)<\frac{1}{2}c_2(G)$ where $l(Z)$ is the length of $Z$?
If not, can we at least say $\leq$ or something? Thank you.