Numbering of simultaneously started NovaSeq runs?

[JakobHedegaard]

How are simultaneously started NovaSeq runs actually numbered?

First time we tried, the A-run was assigned with the lowest number. This would somehow be the logical way of numbering.
190311_A00606_0037_AH7J23DRXX
190311_A00606_0038_BH7KCWDRXX

But next time, the B-run was given the lowest number
190322_A00606_0040_BH7HWVDRXX
190322_A00606_0041_AH7HY3DRXX

Anyone who know the logic behind numbering of simultaneously started NovaSeq runs?

[GenoMax]

Which ever side starts first likely grabs the next numeric number.

[JakobHedegaard]

I have received the following clarifying reply from Illumina Techsupport:
"The run number assignment is sequential to which side actually starts first after the pre-run checks. Usually FCA will have the lower number but sometimes if something fails on the pre-run checks, the software will automatically retry the failed test which adds time and can result in the run starting later compared to the other side."