The string appears to refer to the character , better known as
: In high-end design, AMA10 is the specific model code for a beige matte wall tile ( -ama10- 7- -4-
This implies the missing number is actually -7 + 3 = -4. However, I think there might have been a typo in your question. If we assume the correct sequence is an arithmetic progression with a common difference of 3: The string appears to refer to the character