Currently, if you are convicted of a First Degree Robbery, a class A felony in Washington, and you have no criminal history, then your standard range sentence would be 31 to 41 months. If you have prior felonies, or other being sentenced on other offenses at the same time, that standard range will increase.
If you are convicted of First Degree Robbery, and were armed with a firearm, you may get 5 additional years for using a gun during the robbery. That time is consecutive to the standard range and you get no good time off of it.
If this armed robbery is your third "strike" you get life in prison with no possibility of parole.