Any closed system or tank can be overfilled and doing so can prove to be dangerous or can rupture your tank and ruin your equipment at the least. Look up hydraullic pressure on a search engine to learn more about this.
Both the Extractor Tank and Recovery Tank can be filled up to the shoulder of the tank. The shoulder of the tank is the max fill line when filling with liquids. The top area above the shoulder of the tank is the air buffer zone. This top area should never be filled with liquid. When inverting the tank the air buffer obviously moves to the top as oriented.
TE175 system can hold 700 ml or 400 grams of pure butane solvent.
TE700 system can hold 2800 ml or 1600 grams of pure butane solvent.
Remember that grams are for weight and milliliters are for volume or space occupied.
If mixing butane with other solvents you will need to know what a milliliter of that solvent weighs to properly calculate the exact volume that solvent will take up in the tanks. Then adjust accordingly.
If you use water for example, 1 milliliter of water weighs 1 gram. 1 milliliter of butane weighs .577 grams.
Meaning a gram of butane will take up more space than water.
If you fill up with 400 grams of pure water you will only take up 400 milliliters of space in the tank. Way under 700 and very safe.
To over fill when mixing butane with other sovlents you would really have to miscalculate.
