Community Bible Fellowship of Aberdeen

Hello! So I was doing a few setup practice drill problems in the Logic Game bible under the section "grouping". Though I fairly understand the rules, I'm a bit perplexed with number 6 (on page 320). When I was mapping out the rules "If he does not choose H, then he chooses L" I did it the way the book says to in the answer key by doing H(not) :arrow: L, and in the SAME way I diagrammed the rule "If he chooses M, he does not choose L" as M :arrow: L(not), how come in the answer key, the diagram for the sixth rule is using double not arrows but for the fifth its a single arrow with a simple negation? Thanks I didn't find the right solution from the internet. References: https://forum.powerscore.com/lsat/viewtopic.php?t=14521 2D Promotional Video