Watches your chat box for “The effects of overload are about to wear off.” and alerts you. Keep chat text at the default size.
Advanced — buff bar timer
Lets you pick exactly when to alert, instead of the game’s fixed ~20s chat warning. Requires RS3 Buff Bar Size: Small and Game/UI Scale: 100% (Settings › Display) — Alt1 can’t read buff icons at any other size.
Not calibrated
Drink an Overload potion so its icon is visible in your buff bar, then click Calibrate and pick it from the icons shown.