AM5726: Clarification required on sprac76a.pdf

Part Number:AM5726

Hi,

Few questions on the document:

1. Example PCB stack up for AM5726 provided in the above document shows target impedance for different types (stripline, microstrip, surface etc). None of the target numbers correspond to the DDR3 target impedance specified in the Table 8-6 in the datasheet (50-75 Ω). Are they not listed in the table? Why?

2. What "EC Microstrip" impedance in lines 13-15 on page 21 are ? (values 110.77, 87.59, 87.60) Where are they used?

thanks

Michael