You have quite a few errors in your library files. You declare a member function with the name of setTimer yet within your cpp file you call it Set. Furthermore you omit the “void” in front of the function definition.
I’m not even sure what you mean by this line.
int x = (time_ms*1.5625); Are you trying to use a template or perhaps attempting to cast the result of a calculation to a static type?
I’m sure you’d be all over this if you had your environment setup correctly.
Here’s how I suggest you get started.
Open the IDE
click the down arrow on far right hand side of the IDE and select “New Tab”
Enter the name as AllTimer.h
Do the same again to create another tab named AllTimer.cpp
Now you can click on the separate tabs to enter your code in the relevant files
When you hit compile all three files will be compiled and show you your errors and warnings accordingly.
Once you have your library files working to your satisfaction you can close the IDE
Create a separate directory (within your libraries directory) called AllTimer
Copy the .h and .cpp files from your original sketch directory into this new directory, and there you go.
BTW Happy new year!