See two Rems after uploading a local pdf file. How to only keep one?

Hi RemNote,
I am new to using RemNote and may be confused with one feature.
I tried to upload a local pdf file as a reference. I expect that it can be a Rem and I can link it when I want. But I can see two Rems in the All Note page after uploading the file. One is named XXXX.pdf and the other is named XXXX which is the Rem that contains the pdf file. May I ask how could I remove one of them and just keep one, either XXXX.pdf or XXXX, in my workspace.
Thank you,