"מְכָרוּהוּ בֵּית דִּין עוֹבֵד שֵׁשׁ שָׁנִים ... אֲבָל אִם פָּגְעָה בּוֹ שְׁנַת יוֹבֵל אֲפִלּוּ נִמְכַּר שָׁנָה אַחַת לִפְנֵי הַיּוֹבֵל הֲרֵי זֶה יֵצֵא לְחֵרוּת :
If the court has sold him, he serves six years ...
IF, however, the jubilee year intervenes, even though he was sold only one year before jubilee, he goes free..."
As I understand the 50th year WAS perfectly predicted, and everybody knew the counting. So Rambam should have used the language of "When the slave is sold less than 6 years before the Yovel" because his price will surely go down accordingly, and not "If Yovel intervenes". Rambam sounds like "if he was paid the full price but Yovel suddenly came, he breaks free".
"How this Rambam's"IF" of "the jubilee year intervention" can be explained?