The metadata in the SRA is not all the data you can get about a run. Here is how to get more data about a run from the SRA without going to the SRA website.
The SRA metadata has lots of information about the sequences, but unfortunately it does not have information about the runs such as how many reads there are, what the average run length is, or the total size of the data set. This makes it tricky to try and plan ahead. Luckily there is an API that allows you to access this data for all the runs.
If you have the sra tools installed (and you should!), then the vdb-dump command is your friend. For example, lets look at SRR3280498.
$ vdb-dump --info SRR3280498 acc : SRR3280498 path : http://sra-download.ncbi.nlm.nih.gov/srapub/SRR3280498 size : 269,650,849 cache : /home/redwards/ncbi/public/sra/SRR3280498.sra percent: 0.097182 bytes : 262,144 type : Database platf : SRA_PLATFORM_PACBIO_SMRT SEQ : 76,757 SCHEMA : NCBI:align:db:alignment_sorted#1.3 TIME : 0x0000000056f1cf52 (03/22/2016 16:03) FMT : FASTQ FMTVER : 2.5.7 LDR : latf-load.2.5.7 LDRVER : 2.5.7 LDRDATE: Dec 21 2015 (12/21/2015 0:0)
This is a PacBio run that has 269MB of sequence in 76,757 reads. The average read length is 3,513 bp.