Intermittently, monitoring system shows that 2x10G reth (or ae) interface throughput is showing spikes that exceed the maximum 20Gbps.

user@SRX> show interfaces reth2 
Physical interface: reth2, Enabled, Physical link is Up
  Interface index: 128, SNMP ifIndex: 599
  Link-level type: Ethernet, MTU: 1514, Speed: 20Gbps ...
...

user@SRX> show snmp mib walk ifHCOutOctets | match "ifHCOutOctets.599" | refresh 30 
...
Mon Jan 22 16:04:57
ifHCOutOctets.599 = 573517292570
Mon Jan 22 16:05:27
ifHCOutOctets.599 = 936104374242  <<<< (936104374242-573517292570)/30*8/1024/1024/1024 = 90.05 Gbps
Mon Jan 22 16:05:57
ifHCOutOctets.599 = 1006892479242 <<<< (1006892479242-936104374242)/30*8/1024/1024/1024 = 17.58 Gbps

To resolve this software issue, upgrade to a release which has a fix for PR1706125 (https://prsearch.juniper.net/problemreport/PR1706125).