There is the same notation in the name of the christening entry 100--Oltmann Ulfers. The Ancestry.com transcription does not indicate any tilde over the final "n" in Oltman's name, while there is one in Anna's. My suspicion is that this is likely because tildes are not often used at the end of any word. The tildes are not used in the transcription of Tamme Tammen's name. This may be because tildes are not usually used with the letter "m."
The interpretation of the line above the letter is inconsistent and it's pretty clear that the same symbol is being used in "Oltmann," "Anna," and "Tamme Tammen."
Learning various writing conventions and shorthand takes time. Understanding these conventions also requires some knowledge of local names so that these conventions can be interpreted correctly. I can't overemphasize the importance of becoming familiar with the records being used and manually searching those records--even when indexes are available.
Have you thought about dropping the second double letter in a name when querying a database? Did the creator of the record you are using an index for use a notation that a transcriber handled incorrectly? These sorts of issues are not only encountered with church records written in the German script.
Note: Screen shorts of Ancestry.com screens are current as of the date this post is published.