  This paper presents detailed consideration of methodologies to calibrate
differential light curves for accurate physical starspot modeling. We use the
Sun and starspot models as a testbed to highlight some factors in this
calibration that that have not yet been treated with care. One unambiguously
successful procedure for converting a differential light curve into a light
deficit curve appears difficult to implement, but methodologies are presented
that work in many cases. The years-long time coverage of Kepler provides a
strong advantage, but unresolved issues concerning the competing and sometimes
similar effects of surface differential rotation versus spot number and size
evolution can prevent the confident recovery of correct spot covering fractions
in certain cases.
  We also consider whether faculae are detected by Kepler and/or must be
accounted for. We conclude their effects are such that absolute photometry is
not required for spot deficit calibrations. To elucidate their signature we
re-examine correlations between absolute brightness, differential variability,
and apparent spot coverage for hundreds of Kepler stars with absolute
calibrations from Montet et al. (2017). The results are similar to theirs, but
we draw somewhat different conclusions. Most of the stars in this active
solar-type sample are spot-dominated as expected. Partly because of a dearth of
longer period stars, the evidence for facular dominance in this sample is both
sparse and relatively weak. The facular population exhibits a puzzling lack of
dependence on rotation period, which raises questions about the apparent
detection of a "facular" signal at short periods.
