[isthisLOL?]

Ayumi's chestvoice range goes from F3 to F5, exactly 2 octaves(which isn't bad a for a Pop singer at all, Adele has 1.8 octaves chestvoice and is usually considered good, Lady Gaga is a bit over 2 octaves but practically speaks her lower notes and struggles at the high ones etc.), she might be able to go lower but I can't think of an example of that actually happening. However I don't think she ever belted F5s well live(she has hit them live, but not well), she does do some good E5s live though, so only one note lower.
From around 2005 to 2010 she was unable to hit her high notes(she does sing high at times there, but it's headvoice and mixed voice rather than chestvoice and anyone can reach those notes in headvoice), but she regained them and is better at them than before now, great D5s in BRILLANTE for example and a couple great Eb5s and E5s throughout POWER of MUSIC, notes she avoided ever after AT0304.
That makes her a Mezzosoprano, but she was more amongst the range of an Alto for some time before gaining back her range.

The high notes in kanariya are F5s, they ARE part of what she can sing, however back in 1999 she struggled a lot with them and kanariya is simply FILLED with such high notes, that's why it's so struggled. Some of them are mixed voice rather than chest voice there, too.