Why is the value of specific rotation different in different cases? An unknown compound with a mass of $4.5~\mathrm{g}$ is dissolved in enough carbon tetrachloride to make a total volume of $250~\mathrm{cm^3}$. The observed  rotation of this solution is $+357.75^\circ$ in a $25~\mathrm{cm}$ cell using the sodium D line. But if $4.5~\mathrm{g}$ is dissolved in $125~\mathrm{cm^3}$ we observed  rotation is $+355.50^\circ$. Calculate specific rotation for this compound. (assuming length of polarimeter tube is $1~\mathrm{dm}$)


My approach is starting with the formula stated on Wikipedia.

$$\text{Specific rotation (in first case)} = 
\frac{+357.75^\circ}{\left(\frac{4.5}{250}\right)(1)}=19875^\circ=75^\circ$$

$$\text{Specific rotation (in second case)} =
\frac{+355.50^\circ}{\left(\frac{4.5}{125}\right)(1)}=9875^\circ=155^\circ$$

Any idea why the two answers are different? Did I miss out something?
A polarimeter is typically a long cylindrical tube with flat ends. I think the 25 cm was referring to the diameter of the tube. The other wrinkle here is that the angle measurement may be + or -. So 357.75 may in fact be -2.25. 

Specific Rotation (in first case)=$$\frac{-2.25^{0}}{(\frac{4.5}{250})(1)}= - 125^{0}$$

Specific Rotation (in second case)=$$\frac{-4.50^{0}}{(\frac{4.5}{125})(1)}=-125^{0}$$