N50 is part of their old bin location system that told you exactly where on the shelf the item was. In your example it would be the 50th location in the 14th bay (bay N) on that isle. Here is an example of a bin location on a price label

https://i.imgur.com/E0AUjIL.jpg

As part of their modernization to the product locator system they were supposed to remove all the bin location tags (red triangular flags). If they were in fact removed you can count the bays yourself or look for bin locations on other price tags.

I don't know what kind of genius thought getting rid of fine grained location data and replacing it with coarse locations would help improve the customers ability to find items, but it is typical of Lowe's current leadership. They replace a well designed and efficient solution with a half baked solution and then go on to bungle the implementation of said half baked solution.