'mi' atributte value is always the 100k scale of the MI

[rsmaior]

Just create a grid zone with desired grid zone scale of 50k or 25k and the value of atributte 'mi' will be the 100k scale MI zone.

i.e.: Create the MI 2216-1-NE with desired grid zone scale and base scale both set to 25k. Open the atributte table and 'mi' value will be 2216 instead of 2216-1-NE