I.up [美 əp, 英 ʌp]副up often appears as the second element of certain verb structures in English (back up, pick up, sit up, etc). For translations, see the relevant verb entry (back, pick, sit, etc).
Totaling the rows (adding horizontally) the number of true positives and false positives add up to 100% of the test positives, and likewise for negatives.