I'm trying to understand the following sentence from Leonhard Euler's Institutionum calculi integralis Vol. III Chap. 2, bottom of p.40:
Huiusmodi functiones arbitrarias, prouti hic feci, eiusmodi signandi modo f:y indicabo, unde cauendum erit ne littera f pro quantitate habeatur, quocirca ipsi colon suffigere visum est.
A translation can be found here, but I'm unable to make sense of the second half:
Arbitrary functions of this kind, as I have made here, I will indicate by being marked in this way f:y , from which there will be a caution, without the letter f for the quantity that may be considered, concerning which a colon is considered sufficient.
I'd appreciate your help rephrasing this.
(Some context: The passage is interesting since Euler is largely considered responsible for introducing and popularising the f(x) notation in mathematics, which he at that time wrote as f:x. This is one of the few instances where he explains something about it.)