From Mean Moon to True Moon in an old procedural calendar
How would you interpret this? "(1780 + 80) * 3 on base 808, and add 2"


As before, there is a confusing avoidance of specifying the unit under consideration, but the pattern is still that the last number is in minutes of arc, the middle in degrees, and the first in $30^\circ$ for the Zodiac divisions, so:
$$\begin{eqnarray*}
\frac{(1780+80)\times 3}{808} &amp;=&amp; 6+\frac{27}{30} + \frac{10}{30\times 60} + \frac{41}{30\times 60^2}+\ldots \\
&amp;=&amp; (6;\;27\!:\,10)\text{.}\end{eqnarray*}$$
The $+2$ makes this $(6;\;27\!:\,12)$, although this makes the second addend in minutes of arc while the first one is not. As before, the calculation is not rounded.


  Eade has (8; 11 : 7) - (6; 27 : 12) = (1; 3 : 55), but that doesn't work.
  
  That specific substr. gives me (1; 13 : 55), which could be a typo in the paper, but that value doesn't carry things forward either.


I think that you are correct that this is a typographical error, but the corrected value probably is carried forward--the error is just repeated again in Step 16. Note that $(1;\;13\!:\,55) = 43^\circ 55'$, which makes the corrected Step 16
$$296\sin(1;\;13\!:\,55) = 205.309 = (0;\;3\!:25)\text{,}$$
following the convention that the numerical value is re-interpreted as minutes of arc. On the other hand, if we follow what Step 16 actually says, we get a very different value:
$$296\sin(1;\;3\!:\,55) = 165.164 = (0;\;2\!:45)\text{.}$$

Granted, the value actually carried forward to Step 17 is $(0;\;3\!:24)$ instead, but the former is definitely much closer. This further discrepancy could also be an undocumented geographical correction (the procedure does, after all, have things like $+3$ and $+2$ at times), but I'm more inclined to guess that this is due to imprecision in the calculation of sine, as the paper indicates that a table was used.