Your scan is 300 x 300 pixels, Barry. If you scanned a 1 1/2" chip at 300 dots per inch, your picture would be about 450 pixels square (450 x 450). I suspect you are either scanning at about 200 dpi or you are resizing after the scan to produce a 300 x 300 image.

dpi (dots per inch) is a measure of the resolution of the scan and is related to how many samples of the image the scanner made per inch of size on the original. When you see something like "300 x 300", you are looking at the number of picture elements (pixels) there are in each of the x and y dimensions of the finished picture.

When you right-click on a picture displayed on a Windows screen and select "properties", what you see for "dimensions" is the number of pixels in each of the vertical and horizontal directions on the screen for that picture. You can't tell from "dimensions" what resolution was used in the scanning process unless you know the size of the orignal scanned and the picture has been cropped so the image exactly fills the canvas.