I've done a few of these, and our examiner out here goes with the 30-hour minimum theory.
(3) 20 hours of training on the areas of operation listed in §61.127(b)(2) of this part that includes at least—
(i) 10 hours of instrument training of which at least 5 hours must be in a multiengine airplane;
..is interpreted to mean he needs to log a TOTAL of 20 hours DUAL in multiengine airplanes, including the 10 hours of instrument training; up to 5 hours of previously logged instrument time from other category or class(or FTD, etc.) can be credited toward the 10 total required IFR hours, with at least 5 additional IFR hours logged in the twin. Regardless of how the instrument time is done or how much he needs, he still needs the 20 hours TOTAL dual in the multiengine airplane, since he is doing his initial commercial certificate and not an add-on.
(ii) 10 hours of training in a multiengine airplane that has a retractable landing gear, flaps, and controllable pitch propellers, or is turbine-powered, or for an applicant seeking a multiengine seaplane rating, 10 hours of training in a multiengine seaplane that has flaps and a controllable pitch propeller;
(iii) One cross-country flight of at least 2 hours in a multiengine airplane in day VFR conditions, consisting of a total straight-line distance of more than 100 nautical miles from the original point of departure;
(iv) One cross-country flight of at least 2 hours in a multiengine airplane in night VFR conditions, consisting of a total straight-line distance of more than 100 nautical miles from the original point of departure; and
(v) 3 hours in a multiengine airplane in preparation for the practical test within the 60-day period preceding the date of the test.
..So you have to do AT LEAST this stuff (instrument, x-c, and night), plus fill out the rest of the 20 total required dual hours with other training, which will happen anyway just doing maneuvers and such.
(4) 10 hours of solo flight time in a multiengine airplane or 10 hours of flight time performing the duties of pilot in command in a multiengine airplane with an authorized instructor (either of which may be credited towards the flight time requirement in paragraph (b)(2) of this section), on the areas of operation listed in §61.127(b)(2) of this part that includes at least—
(i) One cross-country flight of not less than 300 nautical miles total distance with landings at a minimum of three points, one of which is a straight-line distance of at least 250 nautical miles from the original departure point. However, if this requirement is being met in Hawaii, the longest segment need only have a straight-line distance of at least 150 nautical miles; and
(ii) 5 hours in night VFR conditions with 10 takeoffs and 10 landings (with each landing involving a flight with a traffic pattern) at an airport with an operating control tower.
..This 10 hours is seperate from the 20 hours of TRAINING (dual) time listed above, and needs to be logged differently; the remarks column needs to reflect "Performing duties of PIC" or some such. An alternative method is to give them the signoff allowing them to act as PIC of aircraft for which they do not hold a rating (see AC61-65) with a limitation that requires an MEI to be on board with them, then let them log that time as PIC. When checkride time comes, remove the restriction.
So I'll say 30, too. Again, this may be interpreted differently by different examiners, so ask around locally if you can, but this is how they do it out here. One of my guys was an ASEL private/instrument rated dude; he built time doing his cross-countries, and we started his multi as outlined above when he got to 220 total time. Did the last 30 as his initial commercial in the twin, then the single-engine add-on afterwards.