A withdrawal limit is a great tool to mitigate the damage that can be done in case your account is breached.
It is not a replacement for having a strong password, and for having 2FA enabled.
How a withdrawal limit works
A withdrawal limit limits the amount that can be withdrawn from your account for X days.
If you set the amount to 0, nothing can be withdrawn until the limit expires.
The expiration date for the limit can be set to any number of days.
If a hacker gains access to your account, he will not be able to withdraw any additional funds past the limit. This gives you some time to regain access to the account before the limit expires.
Adding a withdrawal limit to your account is a non-reversible account. If it could be reversed, a hacker could trivially circumvent it by changing it once he had breached your account.
When should I add a withdrawal limit?
Adding some kind of withdrawal limit is always good practice. You may set it to 10% of your stored funds, or 50% of your stored funds (in case you're more risk tolerant, or think you will need to withdraw large amounts in the near future).
It is recommended to set the expiry to at least a week. That way you will have 7 days to regain access to your account, should your account be breached. The account recovery procedure can generally be done in 1-2 business days.
How to add a withdrawal limit
To add a withdrawal limit, navigate to your account settings and scroll down a bit, until you see the "Withdrawal Limits" field, then click "Change". A dialog box will appear. In this dialog box, you can type in your desired limit (in USD) and your desired expiry. Then hit "Submit".