While avoiding strongly regionally or socially marked forms, they are intended to include the most common variants for each word.Here are some snippets to illustrate what they understand by "most common variants":
1, and (conj.):
2. of (prep.):
The strongform in General American is missing among the transcriptions; however, when you click the "U.S. /əv/", you hear the strongform.
3. him (pron.)
There's no soundfile for the General British weakform /ɪm/.
4. the (adj.)
There are two weakforms in GB, but only one in GA. When you click GB /ði:/ and /ði/, you hear the same soundfile (see waveform below):
5. from (prep.)
The GB weakform is missing; the pronunciation of the GA word contains the LOT vowel.
The addition of soundfiles seems to need some brushing up.