Either is correct because the sentence can be read with either number or seconds as the subject:

There are (a finite number of) seconds…

There is a finite number [measuring the] seconds

You mean an upside down cake upside down?

Ah a fellow electronics I might salvage someday collector! They call us hoarders but one day we’ll replace those faulty caps / learn to micro solder / source a very specific and difficult to find component and then oh boy will we have saved the cost of replacing that thing that we’ve done without for the last several years!