Improve size estimation footnote

Signed-off-by: Graham <gpe@openrs2.org>

archive/src/main/resources/org/openrs2/archive/templates/caches/index.html

@@ -113,11 +113,12 @@
 				unencrypted replacements.
 			</p>
 			<p>
-				<sup id="size">2</sup> Estimated based on the total compressed
-				length of all groups in the cache. The native
+				<sup id="size">2</sup> Sizes are estimated based on the total
+				compressed length of all groups in the cache. The native
 				<code>.dat2</code>/<code>.idx</code> format has some overhead
 				above this, but the <code>.zip</code> file generated by the
-				archiving service will reduce the overhead.
+				archiving service will reduce the overhead, so the estimated
+				size will roughly match the size of the <code>.zip</code> file.
 			</p>
 		</main>
 	</body>