maybe this documents helps:
Table 5. Ordering Information
Service Description Part Number
SMARTnet 24x7x2 S2P
SMARTnet 24x7x4 SNTP
SMARTnet 8x5x4 SNTE
SMARTnet 8x5xNext Business Day SNT
SMARTnet Onsite 24x7x2 C2P
SMARTnet Onsite 24x7x4 C4P
SMARTnet Onsite 8x5x4 C4S
SMARTnet Onsite 8x5xNext Business Day CS
SMARTnet Software and installation-focused TAC support only, no RMA or other TAC support
SW