@Harry: thanks for posting the picture. I added grease today after adding grease last year fall (about 5 pumps). I am always cautious adding grease when I do not know how the seals are set up. In some applications, too much grease will blow out a seal.
Today, I added grease in 5-pump intervals knowing about the indicator hole. I tried to feel the hole at the rop of the axle, but could not feel it. After about 20 pumps, I I saw a thin string of grease come out the top of the axle. It was maybe 1/16 inch thick. Per the picture: add grease until grease comes out the top of the axle. Job done.
First, the hole is tiny, but works as a simple indicator. Second, 20 pumps seems a lot of grease to be added.