single midi file opens four midi channels when I transfer them to reaper

Hi, It has been just a few days I started dowload and using musescore 4.4.2. I write a single channel piece on musescore and export it as midi file. But when I try to import that midi file to reaper, it opens four different channels (three of those channels are empty) I asked some of my musescore user friends to send me midi files. Their midies works without any problem. So I think there is something wrong in my midi settings. I really need help.