How do I display units when doing snmpwalk?

Question

This is a part of my MIB :

callSuccessRate OBJECT-TYPE
    SYNTAX Integer32
    UNITS        "%"
    MAX-ACCESS read-write
    STATUS current
    DESCRIPTION
        "Success rate of call"
    DEFVAL { 0 }
    ::= { call 1 }

When I run snmpwalk -v2c -c public localhost callSuccessRate I get :

MY-MIB::callSuccessRate = INTEGER: 33

How can I display the units at the end of my integer ?

I tried using "DISPLAY-HINT" :

callSuccessRate OBJECT-TYPE
    SYNTAX Integer32
    DISPLAY-HINT        "%"
    MAX-ACCESS read-write
    STATUS current
    DESCRIPTION
        "Success rate of call"
    DEFVAL { 0 }
    ::= { call 1 }

But my output remains the same :

MY-MIB::callSuccessRate = INTEGER: 33