For your Quick Questions & Answers that you asked...
Assuming you meant 920000 as an address when you asked your question, you haven't used as near as much free space as is available~ You would still have about 3/8 of the ROM left to fill up (0xA00000 to 0xFFFFFF). And, as someone answered for you, you can add up to 16 more MB (effectively doubling the space possible, another 0x1000000 bytes. Yes, that's SIX zeros after the beginning 1!).