Good job on the overall shape of your pear and the way you designed your value blocks! As for the issue you're facing, I think it just comes down to the brush you're using. It looks like it's meant to replicate watercolor, and these brushes are generally unpredictable and not very well suited for this type of assignment. One of the things this exercise is meant to teach you is how to fill in large areas with an even tone. If you're doing this digitally, I would recommend using a brush that's similar to graphite (example 1). I'm not sure if Photoshop has built-in pencil brushes (I'm sure you can download some if not), but I know Krita has some nice ones. Just lower the size to how small a pencil point would be and that should do it. Alternatively, if you want to bypass this part of the exercise and just practice getting the values right, then instead of using a pencil brush, you can grab a basic firm-edged round brush, turn off the pressure sensitivity for opacity, lay down your 5-value palette on your canvas, and then draw your pear eyedropping the values straight from the palette (example 2). This way there's no chance of encountering the issue you had with additional values being created from overlaps between your brushstrokes. But I would still recommend trying a pencil brush later to get as much as possible out of this lesson if you're going the digital route. Hope this helps!