I haven't read your link, but I will explain the two terms in Kant. Regrettably, they are not easy to understand or follow, because they are tightly integrated into Kant's philosophy of mind, which is probably unfamiliar territory and understands the mind in a very different way than your average man on the street.
I would suggest you start here with the SEP entry on Kant and space-time. Basic idea is this: For Kant, space and time are things we bring to our perceiving of the world rather than things we get from the world. There are two interpretations of what he's saying. Kant's detractors and postmodernists primarily maintain the metaphysical reading whereby Kant would be saying that time and space don't exist in the real world. They only exist as mind brings them. Kant's defenders almost all disagree and maintain the epistemological reading whereby what Kant is saying is that for us as human perceivers, we bring time and spaces as forms of sensibility. In strong support of the latter is Kant's refutation of idealism in Critique of Pure Reason.
Building on top of this, Kant thinks that to move from perception to objects we add to the forms of sensibility categories of the understanding. Kant believes there are exactly twelve such categories, conveniently grouped (or contrived) into four groups of three each.
You can read more also on the SEP entry on categories. For our purposes what matters is the grouping called "modality." For Kant, the possible, the existent, and the necessary form a set. And when we have knowledge of an object, we place it under one of these categories. The possible and the potential are synonymous, so when we experience an object under the category of the potential, we believe the object to have capacities not presently realized in time which we would sense as it is realized.