No, its correct.
In the image, substitute the 1s for Is, the 5s for Vs, and the 10 for an X, and the math all adds up.
I + I = II
II + II = IV
IV + V = IX
Or...
1 + 1 = 2
2 + 2 = 4
4 + 5 = 9
So for example, 46 in Roman numerals would be XLVI, which would be 105051 under his system of...