Codes correcting insertion and deletion errors have received considerable attention in recent years due to their applications in DNA storage and other communication and storage systems with synchronization errors. Given two sequences $\boldsymbol{u}$ and $\boldsymbol{v}$, their insdel (short for insertion and deletion) distance is defined as the minimum number of insertions and deletions needed to transform one sequence into the other. Let $I_q(n,d)$ be the maximum size of a code $\mathcal{C}\subseteq \Sigma^n$ where $|\Sigma|=q$, such that any two distinct codewords have insdel distance at least $d$. In this paper, we analyze the upper bound of $I_q(n,d)$ and improve the results from Liu and Xing [IEEE-IT. 69(2), 928-940, 2023].