Each high school may use different weighting systems. So an honors or AP course may be +0.5 at one high school, but +2.0 at some other high school.
Even when states have some sort of standardization (e.g. South Carolina ( https://ed.sc.gov/scdoe/assets/File/districts-schools/state-accountability/NEWUniformGrading.pdf ), or the UC and CSU HS GPA calculations in California ( https://rogerhub.com/gpa-calculator-uc/ )), the different states have different methods.
But that means that when students or parents ask about chances of admission or what colleges will be realistic to apply to but only give a weighted GPA with unspecified weighting, others cannot give good responses.