It seems that the number of monitors depends on the processor (the integrated graphics card in the processor). A little further down on this page you will find how many monitors can be used on a Surface. Note, however, that the information refers to the Surface 3. I don't think the Surface 4 will take any steps backwards here and can do about the same, if not more:
https://www.microsoft.com/surface...
Rocksresort Laax: win a stay for 4 people
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