Ok, if I tap the highlighted '10' two emojis pop up to be selected, a '10' in a box and a smiley face.  If I don't choose either, but continue typing 'pm' then '10pm' is the result.  Again, I cannot duplicate your issue.  It may be an issue with the app version on your Samsung.  You probably should go into Settings and select 'Report a Bug' if you have that option.  It should go to the Developers of that version of the app.