The solffegio frequencies: 396, 417, 528, 639, 741, and 852 do not have the word of caution.
Only the DNA sets: DNA and DNA Nucleotides + WBC RC etc (ALT), DNA Integrity Stimulate (XTRA), and DNA Repair (CAFL) have the word of caution.
While it states contains Solfeggio frequency - use with caution, I would suspect that it is due to the non-solfeggio frequencies that are paired with them, like 731, 732, 537.8, 543.4, etc...
Since this was designed to affect your DNA, and is doing so on the premise of the Solfeggio which not everyone agrees with, the warning to use caution is valid.
If you do not understand the realm of Solffegio and how it is at odds with say the 432 Hz realm, then I suggest a good fortnight of research is in order before you use them.