Hmm...finished my "T" block this morning and had no problems with any of the measurements. I checked my instructions, the HSTs along each side of the "T" should be trimmed to 2.5. String 4 of those in a row, you should get 8.5" (raw edge to raw edge) which should fit the background. The tree blocks should each measure 4.5" square (raw edge). Joining 3 of those together should create a forest 12.5" x 4.5" which should exactly fit across the top of the background after the side triangles are sewn on.
The "middle" row of the tree is half as wide as the top (1" finished vs 2" finished), so at first glance it may appear to be too short when the design is meant to be that way.
My directions appear to be correct for all the blocks this month.
Thank you for your help. I tried a different ruler and the measurements were off just a little on my first cut. Everything seems okay now.