FP does not mean that you are close to your 485 approval. FP is just another step which is part of 485 application.
Read this : (from murhty.com)
If priority dates retrogress after the USCIS has received an AOS filing or the DOS has received a timely CP application, the USCIS or DOS may continue processing the case. For example, persons with pending I-485s, may be called for fingerprinting. This is not a cause for concern. It is also not necessarily connected in any way to the end of retrogression or the priority date becoming current at any point in the near future. It is just a routine part of the case that should be handled in a normal, routine manner.
Anyone with a pending AOS or CP application, who is contacted by the USCIS or DOS for further processing of any kind, whether fingerprinting, Request for Evidence, or any other matter, should respond to the request within the allowed timeframe to avoid a denial of the case. Assuming everything is in order, the case will then remain in pending status until it, hopefully, can be approved once the priority date becomes current.