How can I modify the y axis (individual dissimilarity)

[Carol-Symbiomics]

Hi!
Could you please let me know how can I possibly modify the Y-axis of individual dissimilarity? I do not know why is it much shorter can the coancestry coefficient. I produced this figure using this command.
snpgdsDrawTree(rv2, yaxis.height=T, yaxis.kinship =T)

Also is there a way to modify the scale of these axes? it is undesirable to have a big blank portion in the figure.

Your help is greatly appreciated!