Describe the zoom steps of the tile tab

Tiles.md

@@ -126,8 +126,9 @@ Kind, rate, playback, the solid switch, the collision scale and the sort offset
   it. **Fit** picks whichever draws the tiles larger.
 - For a plain tile the grid is the one tile and the sample map shows it repeated. Both run the
   animation at the set rate.
-- A drag pans the board, the wheel zooms it; nothing on it is edited.
-- **Fit** fills the tab with the board, up to 600 %, so small tiles are shown large. Until you pan
+- A drag pans the board; nothing on it is edited. The wheel zooms in the same steps as the Scene
+  view (12.5 % to 2400 %, counted in screen pixels), so every pixel of a tile is drawn equally wide.
+- **Fit** picks the largest of these steps at which the whole board fits the tab. Until you pan
   or zoom by hand, the board fits itself again when the tab is resized or the tiles change size.
 - The **picture list** on the right is the animation: **+ Picture** adds a texture or a frame,
   **Remove** takes the selected one out, and dragging a row to another place reorders the steps.