fix: one size for the ticked systems on the plan

With systems ticked since the check, the headline counted them (About
3479 files, 82.2 MB) and the Install row kept the whole list's size
(Install 6.6 GB). _ticked_estimate is the one count both read, offline
the files the folders copied from hold.

tests/test_install_tui.py

@@ -1722,6 +1722,23 @@ class TicksBarAndPaths(unittest.TestCase):
         rows = install.tui_rows(state)
         return rows[state.focus[state.screen]]
 
+    def test_install_says_the_size_the_headline_says(self):
+        """One system ticked: the headline said About 3479 files, 82.2 MB
+        and the row Install 6.6 GB, the whole list's size."""
+        big = 6 * 1024 ** 3
+        state = checked_state()
+        state.files[0] = {**state.files[0], "size": big}
+        state.check = {**state.check, "bytes_needed": state.check["bytes_needed"] + big}
+        self.assertEqual(install.tui_rows(state)[0].label, "Install 6.0 GB")
+        for system, label, head in (("nintendo-gba", "Install", "About 1 file, 16.0 KB"),
+                                    ("sony-playstation", "Install 6.0 GB",
+                                     "About 3 files, 6.0 GB")):
+            with self.subTest(system=system):
+                state.ticked = {system}
+                self.assertTrue(install._tui_estimating(state))
+                self.assertEqual(install.tui_rows(state)[0].label, label)
+                self.assertIn(head, "\n".join(install.tui_view(state, 80, 24)))
+
     def test_the_filter_never_changes_the_ticks(self):
         state = self.systems()
         press(state, "n")