EX can only count packet sent to the kernel ( BCM limitation )
https://kb.juniper.net/InfoCenter/index?page=content&id=KB16185
jlk@ex4600-1# show | display set
set firewall family ethernet-switching filter inputethfilter term first then count inputethcounter
set firewall family ethernet-switching filter outputethfilter term first then count outputethcounter
jlk@ex4600-1> show configuration interfaces ge-0/0/1.456 | display set
set interfaces ge-0/0/1 unit 456 vlan-id 456
set interfaces ge-0/0/1 unit 456 family ethernet-switching filter input inputethfilter
set interfaces ge-0/0/1 unit 456 family ethernet-switching filter output outputethfilter
jlk@ex4600-1> show firewall filter outputethfilter
jlk@ex4600-1> show firewall filter inputethfilter
filter for IP:
set firewall filter dasad term sdasd from source-address 0.0.0.0/0
set firewall filter dasad term sdasd then count mycounter
set interfaces ge-0/0/1 unit 456 family inet filter input dasad