Hi I was just hoping someone could help me sort out the conditional logic in this stimulus. I feel like there's a gap in my understanding of the first sentence of the stimulus.

The first statement is about archaic spellings being preserved if they are infrequent and do not interfere with reading comprehension. I think the negation of preserved is modernized.

F: frequent

I: interfere

M: modernize

I originally diagrammed this statement as:

/F & /I -> /M

M -> F or I

The correct diagram is:

/M->/F & /I

F or I -> M

What is the difference I'm missing here?

https://classic.7sage.com/lsat_explanations/lsat-51-section-3-question-19/