Sperners lemma how to mark internal vertices

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Was reading sperners lemma from this

http://www.math.hmc.edu/funfacts/ffiles/20001.4.shtml

Couldn't understand certain things

How to mark internal vertices?

I could have mark some other number for the internal vertices and get another result!

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In Sperner's Lemma, the only restrictions on the vertex labeling are for boundary vertices. Vertices which are in the interior of the triangle (or the simplex, in general) can be labelled arbitrarily.

Indeed, this is the real power of the theorem. As you mention, it is easy to imagine that some labeling of the interior vertices would falsify the conclusion. However, it turns out that any labeling of the interior vertices allows you to find a fully-labeled simplex (a "baby (123) triangle").