A millionaire is read as abundance, security and the freedom money seems to buy. Dream books take it as a wish or a worry about worth, not as a forecast of wealth.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.