For some reason I seemed to be able to pay the exact amount of points needed when booking an Ibis Styles sometime ago. This must have rather been reintroduced to limit the convertability of points - otherwise, each and every point anybody ever earn would be converted and that would cost Accor more money

Overflow points over the 2000 multiples can be converted to airline miles - turn on the automatic conversion just before the end of month, let it convert, and turn it off once it does.

BTW, don't book Sofitels with points, this is, pardonnez-le-mot, pointless. You earn very well paying for Sofitels, but you earn very little in Ibis, Ibis Styles and Adagios. The wise thing to do is pay for all upmarket brands (esp. when there is a special offer with more points) and pay with points for the basic brands.