Target cluster does not have enough free space - reloading sample data

I was on the last ticket for chapter 3 and I made a mistake in the migration of string to datetime.
I accidentally changed the date from a string to an object with doc_id and lastupdated.

Since this wiped out the string data I thought I would have to reload the dataset.

So I went into Compass and deleted the sample datasets and then tried to re-load them but when I do I get an error saying not enough free space.

When I look at the status it shows the size as zero:

What do I do now?

Do I have to wait for the sample data to be deleted from all nodes before I can re-upload? or am I just stuck with no way to re-load the data and finish the class?

I found that it takes some time (15-20min) and then I can reload the data.