You know that is an overflow tank, so even at the low level there is plenty in there as long as it is above the hose, you should have waited to get the real coolant. I take pictures of my engine compartment so I can reference all the fluid levels at different times, mine has not budged in 7500 miles.

 

You know that is an overflow tank, so even at the low level there is plenty in there as long as it is above the hose, you should have waited to get the real coolant.

Sadly OP does not know.

You should really never need to top off inverter or radiator reservoirs if filled to proper levels and over course of coolant maintenance schedule:
10yr/100k 1st drain/fill,
then every 5yr/50k mile drain/fill

if you do, there may be a leak, or another problem in cooling system. The BEST check for radiator coolant level is to revove the radiator cap and verify the coolant is to the top. Checking the radiator overflow wont tell you there is a problem at the radiator, esp if there is lack of vacuum (the overflow will remain unchanged, but level in radiator will be low). Remove radiator cap when the car has cooled sufficiently (many hours or overnight).

 

Tank level will vary a little depending on temperature. If you have to frequently add fluid during your bi-weekly service checks then cooling system may have a leak and require service.