Having trouble reading a chart

I just bought a book with great patterns and I’ve looked up how to read the charts but I must be doing something wrong.
The chart shows 10 purls then a left leaning increase and a right leaning increase then 10 purls.
but the increases obviously add two new stitches. What do I do with them to keep the pattern symmetrical?

A knitting chart essentially shows the result of the finished row, so there should be 22 boxes in that row.

The chart should accommodate the increases on the next row by getting wider. If there are decreases in the same row to offset the increases, then the chart would stay the same size but the stitches that increase or decrease would change position.

You can try out just the chart stitches if you want on a swatch. Cast on the required number of sts to start and work a few rows to see how it proceeds on the needles.

I tried that, just doing a swatch, but I didn’t do it right. If I wanted to cast on the bare minimum would I do just 20 since the chart shows an end goal (at least for the first couple of rows) of 22 sts, including the two increases? Or do I cast on the number of sts I need at the widest point? It is a cabled pattern so there are several increases later which are just represented with black boxes in the beginning.

Usually the pattern or an explanation near the chart will tell you how many sts you begin with, i.e. work the chart over x sts. If you don’t have that, then count the number of sts you would need to do row 1 of the chart. Count 2sts if there’s a decrease in the first chart row. Don’t count the increase sts in row one.

It may be a good idea to cast on about 24 sts, which gives you 2 sts at the beginning and end of the row that aren’t involved in the chart at all. Then just follow the chart - it may help to use markers inside the edge sts so you just have 20 sts between them to begin the first row, that way you won’t be confusing the extra edge stitches with the chart stitches.

Thanks very much!