To make one of those "stepped exposures" on the paper, you need to guess at the correct time so the steps straddle that guessed time. I don't waste my time on that "stepped exposure" anyway because the premise of evaluating different exposures on different parts of the image does not make sense to me.
This, a thousand times this. I don't get how people try to judge exposure by looking at different exposures on different parts of an image. Much better (though it takes a little longer to make the exposures) to make a bunch of test tiles - they each cover the same critical area of the print (e.g. a highlight or face or whatever) and each gets a single exposure of the appropriate length in the test-sequence.
This is an issue we see constantly in the class darkroom. An exposure in 5-2sec increments is different from a 10 sec exposure. I warn the students, but the lure of a single push of the "print" button is sooooo tempting!
"So I am turning over a new leaf but the page is stuck". Diane Arbus
I don´t use the "stepped exposure" method. Instead, I expose the same part of the image several times on the test stripe, using different exposures. (eg. 5, 10, 20, 40 sec). I use a sheet of cardboard with a rectangular hole about 1x3" cut in the middle for this. This allows me a better comparison of the result (on the same part of the image) and eliminates the issue with the lamp warm up time. The test stripes are always 100% like the final result with MG IV. With fibre paper however, there is still the dry down effect...