Confused with 2 SRA runs for one sample


Hello, I am completely new to Sequencing and programming (and I am blonde) - so please bear with me.

I already saw that there are some questions about it, but I could not really understand/deduce what I have to do now.
So, I have the task to recreate some figures of a paper with RStudio. I choose the single-cell RNA-Seq results from this paper:
I already downloaded all SRA files via the SRAtoolkit and I am already converting them in FastQ files with the split-3 option. And I know I have to check them with FastQC afterwards.
But, there are for each sample two SRA runs (this sample for example:] )
Why are there 2 SRA files, which will result in ultematively in 4 FastQ files for one sample?
I have read somewhere "technical duplicates", but there is also this huge difference in size (6.9 GB and 18.3 GB) and if I am clicking on the runs to get more informations I get lost.

Can someone please explain to me why there are 2 SRA files are and how I should proceed with them?






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