user: Question: What the least quantity having a T2a class?
Columns: ['Class', 'Railway number(s)', 'Quantity rebuilt', 'Rebuild year(s)', 'Type']
Types: ['text', 'text', 'real', 'text', 'text']
Sample row: ['B3', '1"…148', 51.0, '1867–1883', '1B n2']
SQL:

assistant: SELECT MIN("Quantity rebuilt") FROM "Table" WHERE "Class" = 'T2a';