Test 400 refers to the concentration (400mg/mL), and dosages don't vary with concentration, just the amount of fluid you need to inject. What is your age, body fat percentage, training experience?
test 400 is just test man... it just means that every cc you inject, you are getting 400 mg... its going to be a more painful injection with the higher concentration, so keep that in mind... what are your stats? age/height/weight/body fat? goals? cycle history?