PreAnni: detached t for ted, ded, ed

I'm curious about an item in the 1916 manual:

"At the end of many words, ted, ded, and sometimes ed, may be expressed by t being placed beneath or close to the preceding character."   (section 53)   The examples given are

invited     n-v-i / t
divided    dv-i / t
demanded    dm-a-n / t
printed    pr-e-nt / t

What I'm wondering is why the last item isn't pr-e-n / t, and is thus an example of  "sometimes ed." Thinking that the outline of the root verb might be a clue, I looked in a dictionary (unfortunately Anni, as I don't have a dict. for Pre) and found invite as n-v-i, and demand and dm-a-n, but divide is dv-i-d, so the added decoupled t seems to be taking away the d from the main outline in that case, leaving me still uncertain about the case of pr-e-nt / t.

What is the operating rule here?  And / Or ... is there a precise rule, or is this one of those occasional places where we pass the outer limits of systemic exactitude, and into the land of the Free and the Brave?

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