user: Question: what is the maximum number of hull numbers?
Columns: ['Class', 'Ship Name', 'Origin', 'Hull Numbers', 'Service years', 'Previously', 'Note']
Types: ['text', 'text', 'text', 'real', 'text', 'text', 'text']
Sample row: ['Ahmad Yani Class (FFGHM)', 'KRI Ahmad Yani', 'Netherlands', 351.0, '1986–Present', 'RNN HNLMS Tjerk Hiddes(F804)', 'Reportedly still active as of 2009']
SQL:

assistant: SELECT MAX("Hull Numbers") FROM "Table";