On that view only a debt founded on merit conflicts with grace
So they do not think that every kind of debt is at odds with grace, only a debt founded on good works and merits.
When God makes a rational creature, his goodness and wisdom require that he give it the gifts and supply the help it needs to love God with a pure and chaste love and to live a righteous, peaceful and blessed life. Even so, in their view, those gifts and that help belong not to nature but to grace in the proper sense, because they are in no way owed to the creature's merits, and the creature is not equal to them by itself unless God helps it beyond nature.
Latin
XIII. Itaque non existimant debitum omne cum gratia pugnare, sed solum illud quod in bonis operibus & meritis fundatur. Proinde quamvis Deus, dum creaturam rationalem condit, debeat, id exigente bonitate, & sapientia ejus, ei dona conferre, & auxilia praebere quae necessaria sunt ad Deum puro & casto amore prosequendum, vitamque justam tranquillam & beatam degendam, dona & auxilia ista nihilominus, ex eorum mente, non ad naturam, sed ad gratiam proprie dictam pertinent: quoniam talia dona & auxilia nullo modo meritis creaturae debentur, & creatura ex se ad ista non sufficit, nisi supra naturam a Deo adjuvetur.