In Salat what mispronunciations are acceptable?

In salat (prayer) I like to read it out loud sometimes but I whisper it. When I am supposed to say: "sub hana rabb ial 'ala" It comes out like: "sup hana rapial 'ala" Even though it's not what I mean. This is how it comes out when I whisper it. Does this change the meaning of the word and invalidate my prayer? Please let me know.