Doesn't it mean to "Make sure to set that last uint32_t to 1 before each call, to make your map compatible with ACPI"?The format of an entry is 2 uint64_t's and a uint32_t in the 20 byte version, plus one additional uint32_t in the 24 byte ACPI 3.0 version. It is probably best to always store the list entries as 24 byte quantities -- to preserve uint64_t alignments, if nothing else. (Make sure to set that last uint64_t to 1 before each call, to make your map compatible with ACPI).
If so, I guess I'll try to become a wiki editor and fix it.