Total document pages printed double-sided—physical sheets of paper needed (rounded up).
The page takes a positive integer page count and uses ⌈pages ÷ 2⌉ sheets for perfect duplexing (two pages per sheet side pair). Blank back pages on odd counts are implied but not broken out separately.
For an odd total, one back page may stay blank; the sheet count still uses ⌈pages÷2⌉.