Yes, the liquid in the bottle is somewhat viscous and is mixed with water, often 1:4, to make a working solution.
I use other dilutions, e.g. 1:9 for sheet film so if I need 360 ml of developer for 6 BTZS tubes, then I measure out 36 ml of TMAX developer and add the necessary water to make 360 ml of working solution at 1:9. If I were using 1:4, then I would use 72 ml of TMAX developer plus additional water to yield 360 ml of working solution.
Because the volumes are rather low, I usually round up and mix larger volumes of working solution to minimize the effect of measuring errors at low volumes.