clarification about async streaming replication and replication slots

Hi,
I need a clarification about async streaming replication and replication
slots.
I have a master and a standby both with server process running but with
network disconnected between them.

In my primary, I see:
pg_current_xlog_location = B/48DFF790
and, through pg_replication_slots, that standby restart_lsn = B/48DFF6E8.

In my standby, I see:
pg_last_xlog_receive_location = B/48000000
pg_last_xlog_replay_location = B/48DFF6E8

My questions are:
1) why is pg_last_xlog_receive_location< pg_last_xlog_replay_location ?
The standby should receive some parts from master's WAL, write them down to
its WAL and then replay them, right?
2) Can I compare master's pg_current_xlog_location against
pg_replication_slots.restart_lsn
in order to check if the standby is synchronized?
Regards
Pupillo