Anyone can explain the terminoloy in this twitter plot: twitter.com/lymanstoneky/status/1737909661116817666?s=20 Double 5+ Half5+ ?

I think a following tweet explains more: We could double the prevalence of women having 5+ kids or we could cut it in half and the trend in US births since 1975 would be unchanged and the overall level today would still be quite far below replacement or what women say they want.

That doesn't seem surprising to me.