nanopore reads quality is too low

[cfc424]

Hi bro, I am using NanoPlot 1.40.0 to look nanopore data (CRR302667.fastq.gz, downloaded from https://www.sciencedirect.com/science/article/pii/S1672022921001741). My sever is debian system 64bit, and my command is :

nohup NanoPlot -t 10 --fastq ../CRR302667.fastq.gz --plots hex dot kde -o 01.Nanoplot -p Ath -cm Viridis &

Finally, I am confused, and how could I intepreted the following parts (or am I missed something parameters of NanoPlot): (1) my results did not include hex png file, (2) and I also found the statistics summary was somehow different, and I was confused the quality >Q15: 6640 (0.2%) 12.3Mb was really? (3) and Top 5 highest mean basecall quality scores and their read lengths read length is 1?

AthNanoStats.txt content:

General summary:         
Mean read length:                 18,541.3
Mean read quality:                    11.1
Median read length:                7,818.0
Median read quality:                  11.2
Number of reads:               3,064,191.0
Read length N50:                  46,452.0
STDEV read length:                26,536.0
Total bases:              56,814,196,989.0
Number, percentage and megabases of reads above quality cutoffs
>Q5:    3064191 (100.0%) 56814.2Mb
>Q7:    3064123 (100.0%) 56814.2Mb
>Q10:   2168595 (70.8%) 40456.1Mb
>Q12:   1055916 (34.5%) 19383.7Mb
>Q15:   6640 (0.2%) 12.3Mb
Top 5 highest mean basecall quality scores and their read lengths
1:  21.0 (1)
2:  19.0 (1)
3:  19.0 (1)
4:  19.0 (1)
5:  18.9 (358)
Top 5 longest reads and their mean basecall quality score
1:  495032 (12.4)
2:  457760 (8.7)
3:  439434 (9.1)
4:  438143 (8.7)
5:  431286 (9.7)

Thanks in advance,

From cfc424