Sorry, wrong table titles. The first one is Sigma's table, the second one is Sheldon Brown's table:

So, let's present the problem from the beginning ...

Sigma's table:
700x18C 2102
700x20C 2114
700x23C 2133
700x25C 2146
700x28C 2149
700x32C 2174
700x35C 2205
700x40C 2224

Sheldon Brown's table:
Tire Size Miles Km
700 X 44 1382 2224
700 X 38 1355 2180
700 X 35 1347 2168
700 X 32 1339 2155
700 X 28 1327 2136
700 X 25 1308 2105
700 X 23 1302 2097
700 X 20 1296 2086

Now, in the case of 700x35c tires, Sigma's instructions for BC 1606L computer are to enter the number "2205", while Sheldon Brown's instructions are to enter "2168". Both numbers are supposed to relate directly to the wheel's circumference in millimeters.

Why the discrepancy?