Let me be a little clear if I can explain this to you.
Your download speed is capped at 256kb/s and upload speed may be less than that or the same.
Now you say your RDP has a connection of say 30MB/s (30000KB/s).
If you send files (upload) or receive files (download) from your house it will be capped to 256kb/s regardless where your sending the data to.
If you send files (upload) or receive files (download) from your RDP it will be capped to 30MB/s regardless where your sending the data to.
In other words if you are sending data from your RDP to your house ..the max speed you will be able to receive your data is 256kb/s. The max speed that your RDP could possibly send it up to is 30MB/s but that is only if your house connection is able to cope with the speed but in this case is not.
So regardless whether you have RDP or not you can only receive, download, upload, send from ANYWHERE at the same speed your capped to. RDP is used for many purposes and some do use it to upload/download to/from home but everyone has their own reasons (such as security, speed, uptime etc).
Do not assume that just because your RDP does not give you the speeds you were hoping for that is no good. You just had a misunderstanding on how things work. So, if your already thinking that your provider has given you something that you were expecting to get please don't think that way. Only if you were.