The Emancipation Proclamation also only affected areas not under Northern Control.
It did not apply to slaves in border states fighting on the Union side; nor did it affect slaves in southern areas already under Union control.
Not entirely accurate and even where accurate somewhat misleading.
Large areas in the Mississippi Valley and along the Atlantic Coast were occupied by Union forces and not excluded by name from the EP. Therefore slaves in these areas were immediately freed on the EP going into effect. The number was somewhere between 50k and 100k.
The EP also took effect in new areas as the Union armies conquered them. By the end of the war the vast majority of slaves were freed by the EP.
About 250,000 were freed by state action of MD, MO and WV.
Some additional hundreds of thousands were freed by puppet state governments in LA, AR and TN. This was pretty much an extension of federal power and was basically a variant of the EP.
Only about 200,000 were freed by 13A, almost all in KY with a couple hundred in DE.