SNMP with collectd and graphite

I'm trying to move the performance graphs available in the configuration utility outside of the device into our graphite environment. Following the documentation here (https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/tmos-concepts-11-1-0/tmos_snmp.html); here is the relevant part of my snmp.conf for collectd:

    Type "if_octets"
    Table true
    Values ".1.3.6.1.4.1.3375.2.1.1.2.1.3" ".1.3.6.1.4.1.3375.2.1.1.2.1.5"



    Type "if_octets"
    Table true
    Values ".1.3.6.1.4.1.3375.2.1.1.2.1.10" ".1.3.6.1.4.1.3375.2.1.1.2.1.12"

Then in graphite, I'm trying to do this:

diffSeries(lb01.snmp.if_octets.0.tx, timeShift(lb01.snmp.if_octets.0.tx,"-10s"))`

...I'm not yet worried about multiplying by 8 or dividing by 10 because the graphs just simply don't match, regardless of scale. Any idea what I might be doing wrong here?