Yamon3 data usage doesn't match

Yamon is seeing essentially none of my data usage.
The only proposed solution I can find to this issue is SFE, but this is only on DD-WRT (http://usage-monitoring.com/help/?t=sfe). I can't find any similar feature to disable in OpenWRT.
I've tried disabling SQM and I'm still seeing the same discrepancy.
I'm running: LuCI openwrt-19.07 branch (git-20.105.64099-eeba108)](https://github.com/openwrt/luci) / OpenWrt 19.07.2 r10947-65030d81f3

I just tried a fresh install to the latest version (LuCI openwrt-19.07 branch (git-20.136.49537-fb2f363)](https://github.com/openwrt/luci) / OpenWrt 19.07.3 r11063-85e04e9f46) to try and eliminate any other variables. After letting it run for a few hours, the discrepancy much smaller but still significant.