No, I mean tones. Here’s the reason for being precise. If we use the term “note” we have a problem in that there are only 7 of them (A,B,C,D,E,F,G). They then repeat up an octave.
In Gregorian chant the score is written on four lines because it is written for voice. The C Clef mark indicates where the C lies (an F clef marks where F is). However, that is not an absolute. The chanter can “adjust” what “C” means for him or her. It may or may not be “C” (or “F”).
Let’s get a little more technical (if I lose you, let me know). The actual names of the modes are 1) Protus Authentus (First Authentic), 2) Protus Plagis (First Plagal), 3) Deuterus Authentus (Second Authentic), 4) Deuterus Plagis (Second Plagal), 5) Tritus Authetis (Third Authentic), 6) Tritus Plagis (Third Plagal), 7) Tetrardus Authentis (Fourth Authentic) and 8) Tetrardus Palgis (Fourth Plagal). Each of these modes consists of 8 tones (two tetrachords).
Let’s look at the Protus. Protus Authentus has this range: D, E, F, G, A, B, C and D. That’s it. Protus Plagis has this range: A, B, C, D, E, F, G, A.
Each of the other modes has a corresponding range.
Where your confusion seems to be coming in is that you appear to be trying to fit this into your knowledge of later music theory. It doesn’t. You can’t fit the two together. Gregorian chant has its own rules and they predate modern notation.
Deacon Ed