mi probably stands for manufacturer's instructions...
When I helped my installer to put mine in last year he fitted it dry to get an approximate level and to ensure the drain connection could be made - then removed it and put it back down on several generous dobs of silicone - checked and ajusted for level again and left it for 24 hours.
It's only a year now but the 1700 x 690 tray is working well.
Peccavi
August 2009