MCreator issue tracker has been migrated to GitHub.
Existing tickets have been migrated to GitHub. Please open new tickets on the GitHub tracker instead. If you do not have a GitHub account, all feature requests and bug reports from MCreator forums are still considered and checked by the maintainers.
I can't see the screenshot. Try experimenting with group size and mob type in the spawning options.
This might help too: https://www.minecraftforum.net/forums/mapping-and-modding-java-edition/minecraft-mods/modification-development/2341610-needing-a-detailed-explanation-of-mob-spawning