Weekly and by week number (WEEKLY & BYWEEKNO) doesn't work properly

[NaWer]

This rrule has a strange behaviour :

$recurr = new \Recurr\Rule('FREQ=WEEKLY;INTERVAL=1;BYWEEKNO=50,51,52', new \DateTime("2017-10-15 23:59:59"));

$textTransformer = new \Recurr\Transformer\TextTransformer(new \Recurr\Transformer\Translator(config('app.locale')));
var_dump(ucfirst($textTransformer->transform($recurr)));
// print Weekly on Sunday (~ approximate)

var_dump($arrayTransformer->transform($recurr)->toArray()[0]->getStart());
// print 2017-10-15 23:59:59.000000

Excpected :
TextTransformer : Weekly in weeks 50, 51 and 52 on Friday
ArrayTransformer : Fri Dec 15 2017, +7 days, ...