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There are 3 terms mentioned so far that relate to the number of rounds being fired. For two of them, RPM is used as an abbreviation, and you need to know the context.

Cyclic rate
This is the rate the mechanism cycles at. It is expressed in RPM. It is the rate the mechanism will run at if fed a continuous supply of ammunition, but it may not be (and usually isn't) the number of rounds fired if the gun were run continuously for a full minute, since most guns cannot run continuously for a full minute.

A belt fed gun could run continuously for a full minute, with enough belts linked together, something fed from a magazine cannot do that.

The actual number of rounds that can be fired in one minute is "rate of fire", and is also expressed as RPM, but that rate is less them the cyclic rate of the action due to practical considerations.

SO you have to understand the context when someone uses the term RPM. They can be talking about two different things.

Adding to the confusion is people being "conversationally sloppy" using rate of fire when they mean cyclic rate, the way people use engine and motor as interchangable terms in casual conversation when in technical terms they are quite different things.

Also mentioned was "sustained rate of fire" which is a much lower rate, it is the number of rounds per minute that the gun can fire, for long periods of time without overheating and excessive wear. It is something more important to artillery than small arms, generally.