2002 BMW 325 PO128

Engine Cooling problem
2002 BMW 325 6 cyl Automatic 67000 miles

hi,

i bearly change the thermostat on my car, bmw 325i and I took off a blue cap that goes on the bottom of the radiator where the ani-freezer is storage and I let the ani-freezer out but only a small part come out, I guess it did not have that much left or it can be that there is another cap that I am not seeing and I did not let it all out because I can't really see the entire recipient, if is completally empty or not, I bought a new gallon 50/50 of ant-freezer on the bmw dealeship I will like to know if one gallon is in off for the car to work acurate, thanks for any coment will really help.