Schedule maintenance plan

Hello Experts,

Please I need you help,

I share with you a maintenance plan scheduling parameters, my problem it's when I scheduled this plan I don't knw why call date don't correspond to 50% ( Call horizon).

I share with you scheduled calls for a strategy plan ( IP42 ), 1J= 1 Day and 1M = 1 Month and 2 M = 2 Months. You can see the problem, " Plan date ( DatePlanif) = Call date ( Date d'appel ) ", but me I need that the order appear before 50% , for example for Call number 20 I need that the order appear before 15 days " 17.02.2016 " ( Call date ) but it's not the case !!! can you help me please ?!

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Thank you,

Regards,