Weird connection mark result, whats wrong ?

0   ;;; Ping
     chain=forward action=mark-connection new-connection-mark=ping-conn passthrough=yes protocol=icmp 

 1   chain=postrouting action=mark-packet new-packet-mark=ping-up passthrough=no protocol=icmp \
     out-interface=ether1-public connection-mark=ping-conn 

 2   chain=postrouting action=mark-packet new-packet-mark=ping-down passthrough=no protocol=icmp \
     out-interface=ether3-local connection-mark=ping-conn

I want to classify ping packet with connection mark for queue, but in connection track table there are also tcp and udp traffic marked with ping-conn.
Whats wrong with this connection mark?

/ip firewall connection print where connection-mark=ping-conn

Flags: S - seen reply, A - assured 
 #    PROTOCOL SRC-ADDRESS           DST-ADDRESS           TCP-STATE   TIMEOUT    
 0 SA udp      10.3.8.81:59448       206.53.159.132:3478               1m28s      
 1    tcp      103.245.72.54:80      118.97.212.180:48593  established 4h6m52s    
 2    udp      118.82.28.178:55030   192.168.1.172:60582               15s        
 3 SA tcp      10.3.2.244:42432      74.82.90.96:443       established 4m28s      
 4 S  icmp     10.3.3.98             10.3.1.139                        10s        
 5 S  icmp     10.3.3.98             10.3.1.85                         5s         
 6    udp      118.82.28.170:37556   91.236.137.2:61173                4s         
 7    udp      121.187.22.89:21512   118.82.28.178:61495               2s         
 8    udp      190.210.91.1:40489    118.82.28.173:1024                1s         
 9    udp      67.167.137.171:50238  118.82.28.178:54995               1s         
10    udp      157.56.106.189:3544   118.82.28.170:52085               5s         
11 S  icmp     10.3.2.162            118.82.28.237                     7s         
12    udp      159.205.157.52:17401  118.82.28.201:21667               6s         
13    icmp     103.245.72.130        173.252.73.52                     7s         
14    udp      103.245.72.130:26373  195.34.204.246:60020              7s