Took me awhile to locate the 2 documents so I could read what they actually say. But thanks to EWTN, finally found them. For any others who are fussy like me

and want to see the actual texts:
Quanta Cura:
ewtn.com/vlibrary/search2.asp
Syllabus of Errors:
ewtn.com/library/PAPALDOC/P9SYLL.HTM
Since the thread topic connected to these documents has to do with conscience, I think number 15 is the primary statement in question:
III. INDIFFERENTISM, LATITUDINARIANISM
15. Every man is free to embrace and profess that religion which, guided by the light of reason, he shall consider true.—Allocution “Maxima quidem,” June 9, 1862; Damnatio “Multiplices inter,” June 10, 1851.As dmar mentioned, the Quanta/Syllabus is condemning the interpretation of freedom of conscience as it is contained in the referenced document. (Red print above.)
The following article from the Online Catholic Encyclopedia on the syllabus is very helpful Moreover, should a thesis, according to the papal references, be taken from a condemned book, the meaning of the thesis is to be determined according to that which it has in the condemned book. For the thesis has been condemned in this particular meaning and not in any other which might possibly be read into its wording. For instance the **fifteenth thesis, “Everyone is free to adopt and profess that religion which he, guided by the light of reason, holds to be true”, **admits in itself of a right interpretation. For man can and must be led to the knowledge of the true religion through the light of reason.
However, on consulting the Apostolic Letter “Multiplices inter”, dated 10 June, 1851, from which this thesis is taken, it will be found that not every possible meaning is rejected, but only that particular meaning which, in 1848, Vigil, a Peruvian priest, attached to it in his “Defensa”. Influenced by Indifferentism and Rationalism,
Vigil maintained that man is to trust to his own human reason only and not to a Divine reason, i.e. to the truthful and omniscient God Who in supernatural revelation vouches for the truth of a religion. In the sense in which Vigil’s book understands the fifteenth thesis, and in this sense alone does the Syllabus understand and condemn the proposition.
newadvent.org/cathen/14368b.htm
I also found the following website helpful. It went thru the various errors condemned in the Syllabus and then gave an explanation.
matt1618.freeyellow.com/syllabus.html