This KB explains the counter behavior of SNMP OIDs.
The counters on interface statistics does not match with its OID counters
The SNMP OID counters are the cumulative number of the corresponding statistics from the time of the last reboot.
Clearing statistics will not clear the SNMP OID counters. The count just gets added to the previous numbers. The SNMP OID counters gets reset only on a reboot.
root@lab> show interfaces extensive xe-0/0/0 | match over
Oversized frames 100
root@lab> show snmp mib walk 1.3.6.1.2.1.16.1.1.1.10 | match 100
etherStatsOversizePkts.692 = 100
etherStatsOversizePkts.732 = 100
root@lab> clear interfaces statistics xe-0/0/0
{master:0}
Oversized frames 0
root@lab> show snmp mib walk 1.3.6.1.2.1.16.1.1.1.10 | match 200
etherStatsOversizePkts.692 = 200
etherStatsOversizePkts.732 = 200
After reboot
root@lab> show snmp mib walk 1.3.6.1.2.1.16.1.1.1.10
etherStatsOversizePkts.692 = 0
etherStatsOversizePkts.732 = 0