The zoom scale when brushtone loads is automatically set to 32, so 1 pixel will appear as though its 32 by 32 pixels by default. You can zoom in by pressing the insert key, and zoom out by pressing the delete key. To scale it up and correct this, go under the edit menu and select the entire canvas, or select the area of your map, then go under the image menu and use the stretch function, be sure to stretch it evenly by a power of two or it may skew the results, so 64 by 64 would then be 128 by 128, etc.