Opennms Measurement Api ifInoctet value is different than SNMP walk performed

While getting the ifInOctect value for an interface using Measurement API. I value is not similar to ifInOctect when performed snmpwalk
Measurement API -
curl -u admin:admin “[28].interfaceSnmp[eth0-000d3af06e98]/ifInOctets?start=-300000&maxrows=0&aggregation=AVERAGE

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>8422.4341085271328553.706478405315NaN0.0eth0ifInOctets160939410000016093944000001609394700000</time

snmpwalk -v 2c -c snmpcommunity ifInOctets
IF-MIB::ifInOctets.1 = Counter32: 3926269
IF-MIB::ifInOctets.2 = Counter32: 1038941427

Value form Measurement API : 8553.706478405315
Value from snmpwalk : 1038941427

Wanted to understand how do we interpret values is there any additional calculation performed as its only 4 digits?