Update multiple records in MYSQL and PHP

I have several items in a table of my database.
they have numbers to identify their order, and the order system works great.

but if I delete one of these items that is in the middle of the order, then there is a gap in the order and gives me a few bugs.

basically I have this query that isnt totally functional

UPDATE list SET seq-- WHERE seq > '$delseq'

how would i pull off the seq–?
I just need to subtract one from all of the seq values past the one I just deleted.