How to reduce jitter time of IP SLA?

[ปลาวาฬทราย RMUTT CPE IX]

ip sla 10521
 udp-jitter 172.20.235.90 20012 codec g711alaw codec-numpackets 300 codec-interval 200 codec-size 64 advantage-factor 10
 tag Nn

sho ip sla statistics 10521 | inc Jit
Jitter Time:
        Number of SD Jitter Samples: 299
        Number of DS Jitter Samples: 299
        Source to Destination Jitter Min/Avg/Max: 0/302/801 milliseconds
        Destination to Source Jitter Min/Avg/Max: 0/1/1 milliseconds

Thank you very much.

[thecompnerd]

Configure multiple NTP sources if you haven't already.

Despite having NTP sources configured, I still had a similar issue.  Based on separate testing I knew the jitter times were not valid.  Upgrading to the latest recommended maintenance release fixed my problem.