it's all a question about the scales used and how carefully you take a weight reading on yer bow.
i use an easton digital scale. it's extremely accurate. is use the "clothes pin on the shaft" to check the draw length weight. the shaft is a 32" 5/16" woodie, marked at 26" to 31" in 1/2" increments, from the depth of the nock's throat.
when the clothes pin hits the riser i let down. the scaled weight is retained on the easton scale. i do this three times, just to make sure.
imo, analog spring scales just aren't as accurate as digital scales. ymmv.