It is very important to know that the order in which you see a trade depot depends on when each product was placed (date), that is to say, the first one you see (the leftmost one) will be the first one placed (whatever product it is), since they are ordered by descending date.
In the snapshot on the left, you can see 3 cements and on the right, 3 other cements. In the example, the city Atlantis placed first the 3 cements seen on the left, then the 5 donuts, and then the other 3 cements.
In the second snapshot on the left you can see how the Atlantis city trade depot is set up. In this case you can see that the first cement is placed in the third column (first row), and the next 3 cements are not even visible, you would have to move the trade depot to see them.
So, in your trade depot you will be able to put the items in order as it suits you.
And it is very important that, when taking items from a trade depot of a fellow club member, if you have the same products for sale, you should always take the ones that are more to the left.
See also this trick: Sale to Daniel, because it explains one of the many uses of this trick of placing items in trade depot.