In UCP, Is SCTS Field is really consistent between ot-51 ack and ot-53 request?

In UCP, Is SCTS Field is really consistent between ot-51 ack and ot-53
request?

I've been trying to implement a mechanism that communicates with smsc
using the ucp(emi) protocol. on top og that, i was trying to implement a
CDR mechanism, based on three steps: tcp ack, ot-51 ack message and ot-53
notification message. According to the EMI documentation, the SCTS field
should be consistent with the timestamp recieved in the ot-51 ack. i've
noticed that those values are not always consistent, did anyone else came
by this problem? can it be an smsc configuration problem?
thanx in advance :)