The item of data which travels down the most direct path will arrive first. That which goes via satellite will arrive later because it has further to travel.

The ISDN makes no attempt to synchronise the data on the two B channels, possibly because it doesn't understand what the protocol in use. The two B channels are operating independently - the ISDN doesn't care that they're both connecting the same two users.

If the blue data item and the red data item together comprise a logical entity (eg. a picture on a web page), the receiving user cannot use the blue item until the red item has also arrived. It is his responsibility to understand this and to take appropriate action. Normally this will be done in software such as MLPPP.