Minecraft wiki entry for Debug_screen, associated text: Bar chart in the lower left of the Alt + F3 debug screen displays real time measurement of milliseconds per frame with lines marking 16.7 and 33.3 milliseconds per frame, corresponding to 60 and 30 FPS respectively. The graph is color coded from green to yellow to red, with green being faster frame time, red being slower frame time, and yellow in between. In singleplayer and self-hosted LAN worlds (i.e. when running an integrated server), another graph, at the bottom right, shows milliseconds per tick (MSPT) with a line marking 50 MSPT, which is the maximum amount of time a game tick can take while maintaining 20 ticks per second (the intended rate). The color-coding is similar to the FPS graph.