what is the different between single arrow and double arrow

Community PCB Design
1

http://imageshack.com/a/img661/7092/JUtvRt.png

what is the different between single arrow and double arrow in schematic ?

2

I think that the double arrows means that the signal goes to another page.

3

What is the number for? ```
[19]


That to me looks like page number although a 30 page schematic is a biggy :)

Edit: According to IPC-2612A the symbol used is actually a connector, but in this diagram it's not - it's being used for a signal to signal reference that shows that there is another bit of the net elsewhere.

Different people tend to make different use of symbols etc, so what one person sees as an input symbol others will use for an output too.

Or it could be that one is an input and another is bidirectional.