Differences in percentiles when using --base_period with a different study period?

[ngben]

When calculating percentiles, icclim can use the base_period_time_range parameter to set the reference period. If base_period_time_range is not defined, the time_range is used.
I originally calculated the percentiles over the 1985-2014 time_range without base_period_time_range however if I calculate percentiles over the 1979-2021 time range with a base_period_time_range of 1985-2014, there are some very small differences. This plot shows the R95p difference for Jan 1986 between the two

Perhaps I'm misunderstanding how base_period_time_range is applied, I thought that they should be the same within 1985-2014 as the reference period is the same?

I also tested it by recalculating the percentiles over the 1985-2014 time_range with a base_period_time_range of 1985-2014 and this gave the same result as when using the 1985-2014 time_range without base_period_time_range