The original R-179 order (2012) was for 240 4-car sets and 60 5-car sets:
3010-3249 (4's)
3250-3309 (5's).
Some observations:
If pilot is a 10-car train, the numbers may have been reversed in accordance with anticipated production: 3010-3069 (5's) and 3070-3309 (4's).
The live test train in the canned video from March was a 4-car set and I can't see enough of the side view if its the same one.
Note the R-179 "B" end next to the end view of "3019" (paper label). BOM simply "snaps together" 4 or 5 sets as needed for any particular test or inspection with very little difficulty.
Fleet numbers are relative during production. The cars are generic and usually handled by production (i.e. "serial") number until output is finalized for the contractor (NYCT).
The MTA is constantly reviewing the order's quality, construction and content as they always have. It's possible (probable?) that the 60 & 240 formula could be modified substantially by the time deliveries occur. This would involve cost analysis and result in change orders but the cars themselves are designed to be modular in a relative sense. It's a simple matter of how many "A" cars vs "B" cars to produce. Presumably the "B" cars are cheaper than the "A's," (not important) but it seems clear that the NYCT of 2016 needs additional 10-car trains (and more than 6) rather urgently for the November service expansion than it needs (the eventual) 8-car trains for C and J/Z to replace the R-32's and R-42's as planned for the NYCT of 2012 and now aren't being retired anytime soon to enable even more service preservation and expansion.
That's a matter for MTA and more specifically Dept. of Subways to decide, and SOON.
