RE:Supply ship watch........ the "UMKHUSELI"You can't use the vessels draugth to much.
Acc to the vessels spec, it has a Max draught of 7,5 meters in summer water.
E.i. Its most likely already on its normal draught.
Further the vessel could have bunkered fuel, taked stores/provisions for the rig.
And non may be much more than normal deliveries keeping the platform running.
Trips back an forth could something simple like crew change.
The rig workers could do anything from 2-4 weeks.