diff --git a/Firefox-WebExtensions.md b/Firefox-WebExtensions.md
index f1ef5a7..0c3c47b 100644
--- a/Firefox-WebExtensions.md
+++ b/Firefox-WebExtensions.md
@@ -15,7 +15,7 @@ This page may update often until there is a stable release of uBO/webext.
 
 ### First install
 
-The first time uBO/webext-hybrid executes, there might be a noticeable delay (a few seconds): this is caused by the fact that uBO/webext-hybrid will import all the data from legacy storage, into webext storage. This is done only the first time the uBO/webext-hybrid is executed, after this the import step will be skipped.
+The first time uBO/webext-hybrid executes, there might be a noticeable delay<sup>[1]*</sup>: this is caused by the fact that uBO/webext-hybrid will import all the data from legacy storage, into webext storage. This is done only the first time the uBO/webext-hybrid is executed, after this the import step will be skipped.
 
 If you subsequently remove uBO/webext-hybrid, this will cause the webext storage to be removed by Firefox, and upon re-installing the uBO/webext-hybrid version, the import code will again kick in.
 
@@ -23,6 +23,8 @@ Note that uBO/webext-hybrid will still be labelled as "Legacy" in `about:addons`
 
 The legacy storage is left untouched by uBO/webext-hybrid, so you can always go back to uBO/legacy (stable release) if you do not want to use the webext-hybrid version in the short term.
 
+[1] A few seconds on my older than mainstream CPU with default settings/lists. The more filter lists you have enabled, the longer it will take.
+
 ### Firefox for Android
 
 As per [documentation](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Differences_between_desktop_and_Android), only with Firefox Mobile 55 (beta) you can access uBO's popup panel.