To be honest, our calculation of bunches per spur is only approximate.  The result can be made more precise by increasing sample size, but the accuracy depends on how well the sample represents the set of spurs or canes that your pruners will leave in the vineyard.  No sample is perfect.

     Other factors may increase discrepancies between our results and your actual crop load.  For example, the more spurs you decide to keep, the lower the quality of the extra spurs.  That will reduce the average bunch count.  Shoots may sprout out of basal buds where you don't expect them.  Or apical dominance by distal buds may suppress buds below them.

     Our predictions underestimate more often than they overestimate bunch counts.  We do not clearly understand the reason, but it may be that vines are able to rebound after problems.  For example, when many primary buds are lost to necrosis, secondary buds may grow instead.  Perhaps the bunch primordia in the secondary buds are two small for our inspectors to recognize, but are able to grow into usable bunches later.  This problem needs some research.

     Grower's who have a history of several years of bud analysis can interpret their results with more confidence, spotting the bad years and feeling safe in the good years. 

     We are happy to talk over your results with you, and welcome any feedback on how accurate they are for you.