Your target is made up of your Movement Fund pledge, plus the money you'll raise through crowdfunding.
For example, if your crowdfunding pledge is for £5,000, then you need to raise another £5,000 from your supporters. You'd set your campaign target to be at least £10,000.
You need to reach 100% of your target to receive the pledge from the Movement Fund. This is true whether you choose Keep What You Raise or All Or Nothing on Crowdfunder's site.
You can set a stretch target in your dashboard once your campaign is live. You must explain to your supporters what the extra money will be used for.