For card #s 151-200, these are cards that spell out the player's last name.  The serial numbers are specific to these letters which then repeat through this range. 

For example, card#191, Ndamukong Suh, the serial numbers are as follows...

SN001 - Letter S
SN002 - Letter U
SN003 - Letter H
SN004 - Letter S
SN005 - Letter U
SN006 - Letter H
SN007 - Letter S

This is repeated through the end of the serial number range to SN255

SN251 - Letter U
SN252 - Letter H
SN253 - Letter S
SN254 - Letter U
SN255 - Letter H