From type/Supply

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method interval(Supply:U: $interval, $delay = 0, :$scheduler = $*SCHEDULER --> Supply:D)

Creates a supply that emits a value every $interval seconds, starting $delay seconds from the call. The emitted value is an integer, starting from 0, and is incremented by one for each value emitted.

Implementations may treat too-small and negative values as lowest resolution they support, possibly warning in such situations; e.g. treating 0.0001 as 0.001. For 6.d language version, the minimal value specified is 0.001.