An unknown compound weighing $4.5$ gm is dissolved in enough carbon tetrachloride to make a total volume of $250$ c.c. The observed rotation of this solution is $+357.75°$ in a $25$ cm cell using the sodium D line. But if $4.5$ gm is dissolved in $125$ cc we observed rotation is $+355.50°$. Calculate specific rotation for this compound. (assuming length of polarimeter tube is $1$ dm)

MY APPROACH: Using the formula stated here https://en.wikipedia.org/wiki/Specific_rotation#For_solutions

Specific Rotation (in first case)=$$\frac{+357.75^{0}}{(\frac{4.5}{250})(1)}=19875^{0}=75^{0}$$

Specific Rotation (in second case)=$$\frac{+355.50^{0}}{(\frac{4.5}{125})(1)}=9875^{0}=155^{0}$$

Any idea why the two answers are different?Did I miss out something?