Moss Stitch Not Adding Up?

[Drastic]

Hi everyone,

I'm working on the ribbed collar top from ChendaDIY: 

 

I'm on the first part. It uses moss stitch for two rows, then slip stitch back loop only for two rows, then moss, etc. My problem is that at the start of the second row of moss stitch, you chain 1, turn, chain 1, then continue with moss stitch. She puts a stitch marker into the second chain 1. If I don't crochet into that chain ont he next row, and only crochet into the first single crochet, then the end becomes staggered like a staircase. But if I do crochet into the chain 1, then the number of stitches increases by 1, and then you have an even number of stitches and when you get back to moss stitch a couple of rows later it doesn't add up (you'd finish 1 early).

I'm lost. I don't understand how this adds up. Either I don't crochet into the chain 1 when I do the sl blo and I get a staircase edge but my number of stitches remains correct (79) or I do crochet into the chain 1, the number of stitches increases by 1 at the end of every moss stitch section, and then nothing adds up and I probably get the staggered edge when I do the next moss stitch section anyway.

I'm new to crochet and this is my third time unravelling a bunch of this section. The first two times I put the stitch markers where she said and just went from one to the other, but then I had the situation that happened above where my moss stitch rows couldn't end on the last stitch because the number of stitches was even when it needed to be odd. This time I've been counting every row to make sure my stitches stay at 79, but now I'm getting the staggered edge.

Any help would be appreciated. The section I'm talking about is rows 5-6, starts around 11 min in to the video tutorial.

[bgs]

So I looked at min 35 when she lays the front on the back.  The edges at the neckline are not perfectly smooth but have a staggered edge.  Trust the numbers.  I am sure they crochet around the edge which will tidy that up.

[Granny Square]

I didn't look at the video, but when 2 pieces join that aren't rectangles (in other words, there are curves or slanted angles happening), a stair-step edge is normal.  Usually seaming slanted stair step edges together, or crocheting around/over them if it happens at a neckline, will take care of that.