The default values (mainly of Rserie) is adjusted for being as close as possible to the performances of modern PV modules.
In the past (version 5), the default highly underestimated the low-light performances (based on a required gamma value of 1.30 or 1.35).
This had been corrected for the version 6, where the required Gamma was reduced to 1.1 (on the basis of Sandia large database).
But it appears now that this was not sufficient (at least for the recent modules), and I applied a value in a better accordance with all the Low-light measurements I have gathered from official measurements.
However this value is still a little bit conservative.
See the FAQ How should the Rserie be specified ?