Is this traffic shaping valid or make sense?

I am reviewing the QoS config of a router on our network and came across this,

interface Serial2/0.804 point-to-point description 1536kb pvc to Chicago bandwidth 1536 ip address XXX.XXX.XXX.XXX 255.255.255.252 ip summary-address eigrp 646 0.0.0.0 0.0.0.0 180 traffic-shape rate 153600 76800 76800 1000 frame-relay interface-dlci 804 IETF

The remote PVC is a 1.5 Mbps CIR PVC at (Chicago), locally it is a

If we have the target rate is set to 1.536 what benefit is the burst and excess burst values, practically speaking you can not burst above the remote port speed, shouldn't we lower the target rate to (1.536 Mbps - 76.8Kbps - 76.8 Kbps).

Thanks in advance.