Firstly, this spreadsheet is gold, thank you so much for this resource.
Secondly, I'm a bit confused. Shouldn't the "Required Total daily Solar output (Sunny)" - cell L19 calculation which looks at the "# sunny days to recharge (from ZERO) while under load" - cell L18 (as you mention in your definitions, it is the number of sunny days required to recharge the battery from ZERO (or in this case assuming from max discharge) while you are still using power) be referencing the "Battery capacity" - L14 x "max. discharge" - L11 as well as the "Daily Storage Requirement" - cell L10)? You are only considering daily requirements and not replenishing the entire battery in your current formula.
You have: L19 = L10+ L10/L18
Should it not be: L19 = L10+ (L14*L11)/L18
If I'm wrong I may need an explanation why you are not referencing the battery's capacity in a. calculation to full recharge, where a recharge is directly dependent on how much of the battery has been depleted on not only on your daily usage.
Cheers.