riak-erlang-client counter usage

gistfile1.txt

1> {ok, Pid} = riakc_pb_socket:start_link("localhost", 8087).
{ok,<0.35.0>}
2> riakc_pb_socket:set_bucket(Pid, <<"foo">>, [{allow_mult, true}]).
ok
3> riakc_pb_socket:counter_incr(Pid, <<"foo">>, <<"bar">>, 1).      
ok
4> riakc_pb_socket:counter_incr(Pid, <<"foo">>, <<"bar">>, 3).
ok
5> riakc_pb_socket:counter_incr(Pid, <<"foo">>, <<"bar">>, -2).
ok
6> riakc_pb_socket:co
code_change/3   counter_incr/4  counter_incr/5  counter_val/3   
counter_val/4   
6> riakc_pb_socket:counter_val(Pid, <<"foo">>, <<"bar">>).
{ok,2}
7>