You can the following to check the FullForm of your code (makes it easy to understand how Mathematica's internal structures works. Check Mathematica's reference if you want to know details about this.
FullForm[Convert[0.05263, Percent]]
(* Result: Times[5.263`,Percent] *)
There you see that it is a simple multiplication (Head: Times) of two elements. Then you can either use Albert Retey's solution or do a simple
First[Convert[0.05263, Percent]]
(* Result: 5.263 *)
This is especially usefull if you have a more complex output like
FullForm[SpeedOfLight]
(* Result: Times[299792458,Meter,Power[Second,-1]] *)
Then you can do a quick
First[SpeedOfLight]
(* Result: 299792458 *)
to get the value of this expression without the units.
Convertdoes not appear to be a built-in Mathematica function. Are you using a package whereConvertis defined? – DavidC Apr 26 '13 at 12:25