Please correct me if I am wrong, as I understand it, you are inquiring about the "sr" and "lr" settings for "Transceiver Link Type" in C10GX Native PHY. For your information, there is no specific distance value in term of mm for "sr" or "lr". However, at high level, the "sr" setting here is for chip-to-chip interface which the "lr" is for backplane communication. You may refer to the "General and Datapath Parameters" in C10GX XCVR PHY user guide for further details.
Please let me know if there is any concern. Thank you.