What does 0.5 switching cycles / million mean?

I have a similar question regarding the graph on page 273 Section A.6.  This is titled Switching capacity and service life of the relay outputs.  The vertical axis is labeled Switching cycles /million.

What does 0.5 switching cycles / million mean? and how to a relate this to the service life of the relay outputs?  Following the math, is it 2,000,000 million/switching cycle  , if so what does that mean.  

I would imagine that the service life of the relay output should be 2,000,000 operations.

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Split from How many millions of switching cycles can expect from relay output?.

In the graphics, the switching cycles are related to the load. The higher the load, the lower the likely lifespan of the relays. However, there is an upper limit where the operational reliability of the mechanics can no longer be guaranteed even without a load. 2 million switching cycles can perhaps be achieved, but whether they will work for a long time is more of a lottery game...

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