Building the cDNA intron index

[achamess]

I am trying to follow the tutorial to build a cDNA intron index for single nucleus data processing on 10x.

I am following the steps to generate the BED file, but I am not sure where to input the information for the flank size.

Here is what I see on UCSC browser when following the instructions:

Where should I put the L-1 flank?

Also, regarding the input FASTQ files, these are the files that come out after I've run mkfastq in CellRanger, yes?

Thanks!