Make sure context lengths are correct

[M̵̞̗̝̼̅̏̎͝Ȯ̴̝̻̊̃̋̀Õ̷̼͋N̸̩̿͜ ̶̜̠̹̼̩͒]

For 16x16 and under, our max grid cell count is 256, so we could make the context much shorter in this case.