user: Question: What is the sum of the weeks that games occured on october 21, 1974 and less than 50623 fans attended?
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Venue', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'text', 'real']
Sample row: [1.0, 'September 15, 1974', 'Minnesota Vikings', 'L 32-17', 'Lambeau Field', 56267.0]
SQL:

assistant: SELECT SUM("Week") FROM "Table" WHERE "Date" = 'october 21, 1974' AND "Attendance" < 50623.0;