Does anyone know anything about those blue "recurve" draw length measuring bows that shops have?

I was at a farm and home store this weekend, just nosing around, they had one of these hanging so I got it down, pulled it back and asked my daughter to tell me what the measurement was. 27" is where the eye screw intersected the shaft. I let down and pulled back several more times, consistently getting 27".

Are these things set up to account for the + 1.75" from the deepest part of the grip AMO standard, or do I have to add this to the 27" I measured?

I was tempted to walk through the store with the bow to the hardware section and grab a tape measure off the shelf, but didn't