Such a numbering scheme is not part of any 'industry standard' I'm aware of. Indeed, a number like 1.0 Heading implies a Heading 2, but with its numbering starting from 0 instead of 1. If that's the visual effect you want, it's a simple matter to define a numbering scheme that gives you exactly that - and you format Heading 1 as hidden and only use it to force Heading 2 (which you use in its place) to increment.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]