Hello John, (Referring to your email)(posted 8398 days ago)first you pour the required amount of developer stock solution from the bottle into the tank. Shake it. For two 120 rolls measure a total of 30 ml replenisher and add this to the bottle (NOT the tank) Once finished with developing return from tank to bottle, you will loose roughly 15 ml solution per film so your level in the bottle should remain stable. ( 1000 ml bottle - 900 ml for tank + 30 ml replenisher + 870 ml returned from tank is 1000 ml ).
Regards,
Wolfram