$scon and /scon refer to the Nth connection.
$scid and /scid refer to the connection ID. The connection ID increases every time you open a new server window. Connection ID's do not get reused.
For example:
You open up mIRC. The first status window has a connection ID of 1.
You open up a new server (status window) by using /server -m or /server -n. That has a CID of 2
You open up a third server window. That has a CID of 3.
You close the 2nd. The remaining CIDs will be 1 & 3. $scon(1) will refer to CID 1 but $scon(2) will refer to CID 3 because it is the 2nd of the remaining server windows.
