Can anyone help me undestand what the and stands for in this gradient descent explantation?

Summary of gradient descent for multiple regression Contour plot corresponding to 3D plot of RSS init w 0 (or randomly, or smartyl), t1 while ll VRSS(w(t))II > 600 400 for j-o..., DN prtiax)-y(wo) - 20 i=1 w,(t+ 1)