Minecraft wiki entry for effect, associated text: Specifies the effect's duration in seconds (or in gameticks for instant_damage, instant_health, and saturation). If not specified, defaults to 30 seconds (or 1 gameticks for instant_damage, instant_health, and saturation). In Java Edition, any duration greater than or equal to 1639 will display as '**:**' in the player's inventory (while still counting down).
Must be a 32-bit integer number. In Java Edition, it must be between 0 and 1000000 (inclusive). In Bedrock Edition, it must be between 0 and 2147483647 (inclusive), and values higher than 1000000 are treated as 1000000.