Help with bio experiment (about solute concentrations and blood)

[habibibibi]

okay so we had sheep blood, nacl and water

for test tube (all measurements will be in cm3)

A: we put 6 of water, 0 nacl, 0.5 of blood

B: 5 water, 1 nacl, 0.5 blood

C: 4 water, 2 nacl, 0.5 blood

D:3 water, 3 nacl, 0.5 blood

we let it sit for 20 minutes, then we took some, put them in a cuvette and measured it with a colorimeter. (Calibrated at 470nm)

the results were:

A: 1.098

B: 1.349

C: 1.675

D:1.705

okay so i dont really get the meaning of the results, and why did we use a colorimeter?

so what is happening inside if the reading for A was 1.098?

please help