限制JQuery / ajax中的列表选择

Other questions are posted similar to this, but my issue is simply that I don't know where to put the information. That said, I am trying to limit the number of items that are pulled from a list inside of the script below. The script itself works fine, I just need to limit the number of items pulled to six instead of everything. I feel like this is an easy one, but every line of code I inserted from other posts did't work for me. Any help?Other questions are posted similar to this, but