If you are interested in knowing how many nodes are not running any jobs then you can find this out using this command.

cosma-e > cutilisation 
# Free nodes in queue cosma (total=244, closed=0):
m4061 m4084 m4140 m4168 
# 4/244 free

# Free nodes in queue cordelia (total=16, closed=0):
# 1/16 free

# Free nodes in queue cosma5 (total=420, closed=0):
m5170 m5174 m5175 m5176 m5199 m5200 m5203 m5215 m5234 m5250 
# 10/420 free

# Free nodes in queue shm4 (total=6, closed=3):
cosma-e leda 
# 2/3 free

# Free nodes in queue shm5 (total=4, closed=3):
# 0/1 free


As you can see cosma has 4 free nodes, cordelia has 1 and cosma5 has 10, at the moment. The shared memory queues have some free, but note that 3 are closed. These may be closed for adminstrative purposes, or more likely they are too busy to accept any jobs at present. Note that much of this information is also shown by the showq command.

For the cosma and cosma5 queues although nodes are shown as free, all that means is that they are not running any jobs, to make use of those you will need to meet the time constraints of the backfill window on them (which can be unlimited when the queues have no pending jobs).