Meaning of "one with a huge 8, another labelled “1 in 1”"?

Hello everyone. I am reading a novel, and I came across this expression. Could you please let me know its meaning?

A row of scraggy poplars seemed to rise sheer from a blackened coal yard, and looking up a street he could see there had been some kind of accident for there was a crowd and a policeman. But it had gone in a flash, and the chief things now were the mystery signs of the railway. Baby signals beside the lines: tiny little things a foot high, that looked as if they had only just been set: posts with baffling numbers on them: one with a huge 8, another labelled “1 in 1” which seemed to Ernie a stupid claim, for it looked exactly like the other posts.

- R. C. Sherriff, The Fortnight in September, Chapter 7

This is a novel published in 1931, which describes a fortnight in September in which an English family consisting of Mr. and Mrs. Stevens, Mary, Dick, and Ernie go on a holiday. Ernie, the youngest, is looking out of the window of a running train to mystery signs of the railway, which is the source of wonder to him.

In this part, I am not sure what the underlined expression means.

What would mean that there were posts around the railway, to which numbers such as "8" and "1 in 1" were painted...?

*(By the way, this is just my small question, but I also wonder what are those "baby signals" at the beginning of the sentence. )

Thank you very much for your help.