Have you reached agreement with your ex about costs? Costs can include both the legal fees and the court fees. It is however only the costs relating to the divorce itself - it does not cover costs related to sorting out financial issues or issues around any children.
If you leave it in,you can always chose at a later date not to pursue it (e.g. when you apply for the Decree Nisi, if your husband/wife has co-operated)but if you cross it out you won't have the option to put it back in.
It is fairly usual to put the claim for costs in an delete it at the special procedure stage. This gives some leverage to the Petitioner to remove the claim on the agreement that the Petition proceed by consent.