I'm an R novice and working on project with script provided by my professor and I'm having trouble getting an accurate mean for my data that matches the box plot that I created. The mean in this plot is below 300kg per stem and the mean I am getting when I use

ggsummarystats( DBHdata, x = "location", y = "biomassKeith_and_Camphor", ggfunc = ggboxplot, add = "jitter" )

or

tapply(DBHdata$biomassBrown_and_Camphor, DBHdata$location, mean)

I end up with means over 600 kg/stem. Is there way to produce summary statistics in the code for my box plot.

Sample data:

data(PlantGrowth)