Trying to delete a firewall rule

If I run 'show firewall' I ge tthe below output:

IPv4 Modify Firewall "SOURCE_ROUTE":

Active on (eth1.11,IN)

rule action proto packets bytes
---- ------ ----- ------- -----
10 modify all 0 0
condition - saddr 10.10.10.0/27

20 modify all 0 0
condition - saddr 10.10.10.64/29

10000 accept all 0 0

I am trying to delete this, but it says:

delete firewall SOURCE_ROUTE rule 10
The specified configuration node is not valid
Delete failed

If I try and use tab it doesn't show as an option:

delete firewall name
GUEST_IN GUEST_LOCAL WAN_IN WAN_LOCAL

How do I delete these rules?