Rationale for T3580 backoff

[LSKhappychild]

Hi @linouxis9,
Thank you for your great work!

I found that whenever T3580 timer expires, it sets backoff value as math.Pow(5, float64(pduSession.T3580Retries) seconds.
I could not find any related details in 3GPP standard, so could I get any rationale for setting backoff value for T3580 as such?

Thanks!