The Utilized column shows FIT calculations considering only resources that the design actually uses. Since SEU events in unused resources do not affect the FPGA, you can safely ignore these bits for resiliency statistics.
Additionally, the Utilized
column discounts unused memory bits. For example, implementing a 16 × 16 memory in an M20K block uses only 256 bits of the 20 Kb.
Note: The Error Detection flag and the Projected SEU FIT by Component report do not distinguish between critical bit upsets, such as fundamental control logic, or non critical bit upsets, such as initialization logic that executes only once in the design. Apply hierarchy tags at the system level to filter out less important logic errors.
The Projected SEU FIT by Component report's Utilized CRAM FIT represents provable deflation of the FIT rate to account for CRAM upsets that do not matter to the design. Thus, the SEU incidence is always higher than the utilized FIT rate.