In Japanese there are two words for some numbers. For example number 4 is yon or shi and for 7 it is shichi or nana. For announcements on train platforms they do not use shichi, because it sounds like "ichi", which is the word for 1. Also, I think they do not use "shi" for 4 for the same reason. (I hope I got this right, have not studied Japanese for 25 years).
Maybe someone from Japan can clarify if the are talking about the English word "number 1" or if they mean the japanese term "dai ichi".
Maybe someone from Japan can clarify if the are talking about the English word "number 1" or if they mean the japanese term "dai ichi".