You'll notice that the Type I and Type II stamps are only listed on the stamps with the "y" in the catalogue number (45y, 46y, etc.). These "y" stamps are the stamps with the vertical laid paper lines ("x" stamps have horizontal laid paper lines). The "Unterdruck" you're questioning is usually called the "groundwork" in English - the groundwork is the faint dots and lines in the background of the stamp. If you look at the stamp below, you can see this groundwork is poorly centred and it spills into the "7"s in the corners. On Type I stamps, the groundwork is like this one, printed all the way around the "7" value tablets, leaving just a small circle behind which isn't supposed to have any groundwork. On Type II stamps, the groundwork is not printed in the corners.
When the groundwork is poorly centred like on this stamp, you can see easily that it's printed around the value tablets. When the groundwork is nicely centred, you have to try to figure out if the groundwork is printed over top of the dark ink around the value tablets. Difficult! Hopefully you can see the year on the postmark, that can help to rule out the later Type II stamps.
Note - this stamp isn't actually from the 1889 series but it showed the poorly centred groundwork so I chose this one to use as an example. You can see that on this stamp, the reason for the poorly centred groundwork is because it's actually upside down (notice the clear spot where the crown is supposed to go, it's on the bottom of the stamp, not up where the crown is!).
"When printing stamps of small denominations (from 1K to 7K) of the thirteenth issue, the background of stamps often did not coincide with the frame and was clearly visible in white circles with the denomination designation. To eliminate this phenomenon and reduce the number of defects, the ECGB changed the background of these stamps by removing the colored corners"