Panel 1: We see John holding a bill in his hand and saying that he must make a mental note to pay it; for some reason, this makes Elly smile.
Panel 2: As he puts his jacket on, he says that he's made mental notes to call the drugstore and drop off the clothes Lawrence let behind; this piques Doll-Boy Mike's curiosity.
Panel 3: Some time later, he asks Elly, who's just given Lizzie a bath and is drying her off, why Daddy's always making mental notes.
Panel 4: She looks at us, smiles and says that it's the only way he can read his own handwriting.
Summary: It's been a while since she's taken a swipe at Rod, hasn't it? Since she's so smug about her joke at his expense, she breaks the fourth wall, Lynn clearly doesn't like her husband's indecipherable penmanship.