The spec is from A4000T power supply, the values are calculated from the maximum permissible loads if all ports/slots in use, and rounded up with a large safety reserve.
An A4000D does not use much less power, the original A4000D Rev.B even a few watts more because of the standard 74F and PAL Chips installed there.

If the Board generate the -5V from -12V the -12V line must be able to supply the additional current. The resulting 0,6A doesn't seem much but some ATX PSU can only handle 0,3A at the -12V Line.
This -5V is rarely used but afaik some Genlock in the video slot need it and its also connected to the Zorro Slots and the legacy DB23 Video Connector.

So for A4000TX it should be:

+5V 25A
+12V 10A
-12V 0,6A