  Inflationary attractors predict the spectral index and tensor-to-scalar ratio
to take specific values that are consistent with Planck. An example is the
universal attractor for models with a generalised non-minimal coupling, leading
to Starobinsky inflation. In this paper we demonstrate that it also predicts a
specific relation between the amplitude of the power spectrum and the number of
e-folds. The length and height of the inflationary plateau are related via the
non-minimal coupling: in a wide variety of examples, the observed power
normalisation leads to at least 55 flat e-foldings. Prior to this phase, the
inflationary predictions vary and can account for the observational indications
of power loss at large angular scales.
