Ceteris paribus, Folio note's theta is positive due to accrued interests -- as core also suggested.
Theta, for options, simply captures the time decay and nothing else. Accrued interest on a note is part of the value of the note, and is thus much more akin to the price of the underlying stock for an option than theta.
Ceteris paribus, the value of an option decays as a smooth line to zero. Ceteris paribus, the value of a note decays the same way, though with a sawtooth pattern instead of a smooth line as interest accumulates and is paid. Theta describes the rate of overall decline pattern. I.E., the value of a note is more complicated than the value of an option, but theta is negative for both.