This reminds me about how important it is to have a solid lawyer, and an understanding of the legal ecosystem. Even in cases like this with typos, "respond in ten (10) days" can be quite intimidating, especially when there's a money/legal power asymmetry. In one such case, Monster Cable issued a C&D to a much smaller, Blue Jeans Cable. The founder actually worked in litigation for 19 years and I found this portion of…
Not only am I unintimidated by litigation; I sometimes rather miss it.