The total amount of upload minutes that come with each account is listed on our Pro page. SoundCloud plans can't be combined, so for example: if you purchase a Pro subscription, it will not add an additional 4 hours to your account. If you're upgrading from a free account, it will add 2 hours to the quota of your account. 

Since there isn't an option to add extra upload minutes to your quota, if you want more than 4 hours of upload minutes, you will need to upgrade to a Pro Unlimited subscription.