Q. If someone received Shabbos early (after Plag) and davened Maariv then, does the tefilah count for Shabbos meah brochos or for Friday? How about on Shabbos shaleshudes when benching after the shkiah?
A. Minchas Shlomo (2: 4: 27) writes that it is reasonable that the four blessings of birchas hamazon after shalosh seudos belong to the count of meah brochos of Motzei Shabbos, while the ones recited on Erev Shabbos after plag before the shkiah belong to Friday. A similar view is held by Teshuvos Vehanhogos (4: 60), Betzel Hachochmo (4: 155). They maintain that since we wait until proper night begins to comply with mitzvos like matza and suka, the count begins then.
Horav Shlomo Miller's Shlit'a opinion is the opposite, since if one accepts Shabbos early and davens the Maariv of Shabbos, brochos should also follow and be counted then. The same applies to benching on Shaleshudes., since we mention Shabbos in it.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit'a