All records in the database are documented with source notes. As you observe, the churchbooks are by far the most important source -- not just of Wehdem Parish, but also of the other two parishes of Stemwede, Dielingen and Levern. But there are other sources as well, such as censuses, tax lists, and marriage contracts.
All of the farms of Stemwede were given numbers in the late 1600s as part of increased rationalization of government through census-taking and tax collection. In general, the lowest numbers were given to the oldest and largest farms. As farms were gradually added over the succeeding years, new numbers were assigned. If the number is preceded by the word "by," it means that the family was not the farm holder but rather were landless laborers (Heuerlinge) who were living in a cottage (often not much more than a shed) located on the farm.
The naming customs of this region were intimately connected to land tenure and inheritance. In each generation, one and only one offspring was chosen to inherit the family farm. If the heir was male, then the naming practices were like ours, in that his wife and children bore his surname. But if the heir was female, then her husband and children adopted her surname (that is, the name associated with the family farm). Further, if the male heir died and his widow remarried, the new spouse would also adopt the surname associated with the farm. And if a farm fell vacant because there was no suitable heir in a particular generation, then the family chosen to take over the farm would adopt the surname associated with the farm. In each record in the database where one of these events occurred, I have made a note to that effect.
Your own family tree has two interesting variations of the naming customs. Anne Marie Elisabeth Klanke, born in about 1778 in Brockum, Hannover, was undoubtedly baptized with the natal surname of her father, Strangmeyer. But shortly after her birth, her family relocated to Wehdem Parish, where they took over the Klanke farm at 97 Wehdem. Following custom, the family thenceforth adopted the Klanke surname, even the children who had been born earlier and baptized as Strangmeyer. (It would be good to confirm this by reference to the Brockum churchbook, but it is not available on microfilm and can be consulted only in Germany.)
The second variation is even more interesting regarding the naming customs. Johann Heinrich Lehde, born in 1722, and Anne Margarethe Charlotte Schliekriede, born in about 1727, took over the Hilmer farm at 37 Oppendorf in about 1748 and adopted the Hilmer surname. Their chosen heir was to be their youngest son, Johann Friedrich, born in 1770. But he was too young at the time of their retirement to succeed them, so to manage the farm until he came of age, his oldest sibling, your ancestor, Anne Marie Ilsabein Hilmer, born in 1750, was chosen, with her husband, Hermann Heinrich Lehnker, as "interim" farm holder. During this time, they and all their children bore the Hilmer surname, but when Johann Friedrich came of age and took over the farm in 1797, Anne Marie Ilsabein's entire family resettled to a nearby laborer's cottage and reverted to the Lehnker surname. This is why, if you look for the birth record of your ancestor, Marie Henriette Lehnker, born in 1777, you will see that she was baptized with the surname Hilmer but then married, in 1808, with the surname Lehnker.
It should be noted that these naming practices were virtually universal in much of northwestern Germany until the year 1820, when they rather swiftly converted to the modern practice of use of the husband's surname in all circumstances.
PleI welcome any further questions or comments you may have.