Palace-generated gold goes toward the Base Commerce, as opposed to the +X from Buildings part. It is done this way so that Palace gold can be made into Research or Culture, not just for Wealth/Gold.
If you count up the gold in the main City Screen area, you will find 18 Gold total (1 bag = 5 coins); and you also get 1 Gold from Trade. Add these two results to the 8 Palace gold, and you get 26 Gold, which is seen in the tooltip as "26 Base Commerce."
Since your Science rate is 100%, 0 of this Gold is turned into Wealth-type Gold; all of it goes to Science instead. The "+5 from Buildings" comes from the Jewish Shrine; it is not "+13 from Buildings" because the Palace income is already counted in the Base Commerce.
Another way of saying all this more concisely is to say that having a Palace changes your Base Tile production from 2/1/1 to 2/1/9, without showing it on the map (instead it's shown in the buildings).
