The addresses of the gap or overlap are shown in hexadecimal numbers. (Hexadecimal is a base-16 numbering system used in programming.) The message tells you the starting and ending addresses of the gap or overlap and recommends two starting addresses for the memory you added on the memory card.
The first recommended starting address is the starting address of the 384KB of on-board extended memory. The second recommended starting address is the ending address of that 384KB of memory. If you reset your memory card to the first recommended starting address, your system cannot use the 384KB of on-board extended memory in your configuration since its address is used by memory on the memory card. By choosing the second recommended starting address, you can include the 384KB of memory in your configuration because the memory you add on the memory card begins where the 384KB of memory ends.
Some memory cards limit the possible starting addresses you can set. See the manual that came with your memory card to determine which starting address to use.
2-30 Running the Setup Program