Very new and green user to Linux !!

I have a device on my db9 serial port and the pts/# value keeps changing everytime I reboot the computer. I have to keep editing the config file to reflect the new number.

Is there a way to save this to remain at only one value all the time ?

Im not even sure what this value is for !
ttys0 is the Com port number, IRQ4 is the Interupt..what is this pts value ??

I'm reading all i can but at this moment its like your first day of reading a different language

Thanks for any assistance