The Rx Buffer Space Allocation shown in the Buffer Setup page in the MegaWizard™ Plug-In Manager for the IP Compiler for PCI Express® megacore, represents the per virtual connection (VC) rx buffer space allocation. This is identified with the label at the top of the page - Rx Buffer Space Allocation (per VC). The total allocation numbers at the bottom of this page, Total Rx buffer space and Total header credits, are also per VC.
The IP Compiler for PCI Express User Guide, Table 1-6, identifies that the Total RX Buffer Space is limited based on the device. This table should read that the numbers in this column represent the Total RX Buffer Space per VC.
This will be corrected in a future release of the IP Compiler for PCI Express User Guide.