i2c bus electrical specification
The datasheet states 20 + 0.1Cb, but it doesn't say in what units 0.1 coefficient is.  This is not uncommon in IC datasheets.  You can still make practical use of the formula.

We can try to back out the units.

\$ \mathrm{ [ pF ] ={\cfrac{[mA] \cdot [ns]}{[V]} }}\$

For the units to match, 0.1 would have to be in the units of \$ \mathrm{{\cfrac{[V] }{[mA]} }}\$.