Rachel I suggest that there is a sequence of “specific words” showing that there is only ONE prophecy spanning Daniel chapters 8 and 9. I'm sorry if I am only repeating ideas you've already heard... I really don't want to weary you. But this (in summary) is our basic explanation linking the two chapters :
In Daniel chapter 8 Gabriel is commanded, “make this man to understand the vision” (8:16) regarding the Ram, the Goat, etc.
Gabriel undertakes his mission, but he is unable to complete it.
Daniel explains the reason : “I Daniel fainted, and was sick certain days... I was astonished at the vision, but none understood it.” (8:27) [Or as it is in Fenton's Translation, “...I was astonished at the revelation, and could not understand it.” Daniel's primary concern seems to have been the timing, because all the other elements seem quite clear.]
Then about 15 years later, Gabriel returns to Daniel and he resumes his work.
Daniel recognizes Gabriel whom he “had seen in the vision at the beginning.” (9:21) This (I think it is clear,) is a direct reference to the Daniel8 vision. (Daniel immediately associated Gabriel with that earlier vision seen in the 3rd year of Belshazzar involving the Ram, the Goat, the Little horn, and the 2300 days.)
And then Gabriel says to Daniel, “understand the matter and consider the vision”. Again, I suggest that this is a call to consider that earlier vision which has come to Daniel's mind. I see no indication that Gabriel is speaking here about a new vision. (No additional imagery of Beasts, etc. is introduced.)
The only piece of the Daniel8 vision that Gabriel did not explain, all those years earlier, was the 2300 evening-mornings. And so it seems quite natural that the angel should now begin to speak about periods of time.