Actually Jim its the last 6 digits that are the sequential production number of _any_ VIN.
But for the Insight they never have gotten past the need for 4 digits

(digits 5 & 6 will be zeros)
And there are some twists and kinks as to the very early numbers e.g. 1-20 of the first model years production anyway. Crash testing and such. Of most main line cars these early numbers would never see the road. How it works in the Insight's case only Honda knows for sure.
HTH!