Resident ratio shows negative number

Create 10 instant in ec2 and install membase server 1.7.2r-15
Create a cluster of 10 nodes
Load 250K items with 200K per item to cluster.
Check resident ratio, it shows negative number.

Crashing process
   initial_call {mochiweb_socket_server,acceptor_loop,['Argument__1']}
   pid <5898.888.0>
   registered_name []
   error_info
         {exit,{error,closed},
              [{mochiweb_socket_server,acceptor_loop,1},
               {proc_lib,init_p_do_apply,3}]}
   ancestors
         [menelaus_web,menelaus_sup,ns_server_sup,ns_server_cluster_sup,
         <5898.52.0>]
   messages []
   links []
   dictionary []
   trap_exit false
   status running
   heap_size 233
   stack_size 24
   reductions 105