Because FPS caps in Roblox aren’t always hard limits — they’re targets. Roblox uses a software-based cap, and depending on system load, vsync settings, or how the limiter is implemented, slight overshooting can happen. Especially on simple maps like baseplates, your system might briefly render faster than the cap before the limiter adjusts.
If it’s not affecting gameplay or causing tearing, it’s nothing to worry about.