consider -

The last time I went to a "Scottish" Ceilidh (run by the Cheltenham Scottish Country Dance Club - but we didn't know that before we got there) - they announced a waltz.

It took half the dance of trying to fit as three-step until we gave up and did the schottische anyways. AFAIK Scots do not dance the French 4 time waltz - and I have only just got the hang (badly) of the 5-time valse. Don't ask!

Yea yea, it is all very logical, but my advice is have a schottische tune ready as well as a waltz just in case they throw that at you. Ask them which they mean.