Specific gravity question

I have checked the FAQ and wiki-brew and can't seem to find an answer to a question that might be really simple. If I have missed a post that answers this please point me in the right direction, but otherwise I was wondering if you guys could help a home brewing novice.
I did a partial grain brew and when I was done and was adding the water to the carboy with the final wort I added until the specific gravity for the mixture was met at 1.058; however, I was not near the 5 gallons, if anything by my math I was closer to 4 gallons. So, I guess my question is did I do the right thing in not adding the full amount of water or should I have ignored the hydrometer reading?
I think in all of this I'm a little gun shy as my past attempts in college although valiant efforts were more watery than full. Thanks for the help. All the best.

Did you take your SG of the wort after the mash and before adding the extract? If your efficiency was lower than what you expected, you could have had a lower SG, requiring less volume or more extract.

It's also nearly impossible to get an accurate SG when adding top off water to the carboy. In that case, I would trust the recipe more than my reading.

Thanks so much for the quick reply. I took the SG reading after I was done with the entire process, after adding the extract and the hops and ready for it to sit in the primary fermenter for a week with the yeast.
So with you saying its impossible to get an accurate reading when adding water, should I have taken the reading at another time? Should I, even though the yeast has gone for 3 days already add more water to trust the recipe more than my reading?
Sorry for all the questions but thank you so much for the help.

jescholler said:

It's also nearly impossible to get an accurate SG when adding top off water to the carboy. In that case, I would trust the recipe more than my reading.

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Not sure what you mean by that.. If you add the water, mix good, there should be no problem taking a hydrometer... unless I am missing something?

With the question above and what you said, would you say to trust the SG reading and not the amount of water added, ie I should have stopped when the SG reading was at the desired reading, even though I was not at 5 gallons, but only approx 4 gallons to avoid having a watery beer? Thanks again for all of your help, this really is great.

Mixing well is the hard part. Revvy explains it best. See this thread, post #4:
https://www.homebrewtalk.com/f14/low-starting-gravity-149086/#post1704204

If you are doing partial mashing, then it's a good idea to adjust how much extract you add based on what your efficiency from the mash and sparge was.

Thanks for the continued help and the reference to Revvy's post.

So with seeing that now I clearly made the mistake of reading too early with the water added not mixing it well, what should I do? Is it too late to add more water since its already fermented in the primary for a 4 days? Will it just come out with a heavier taste? I hope this first batch isn't a loss. Again thanks for everything and helping me along.

I spoke to the company that I got the original mini mash from and they said to go ahead and add more water when I transfer it to my secondary. They said that not having the full 5 1/4 gallons would throw off the taste, so add the additional gallon or so when I transfer. They said the taste should be fine so long as I boil and cool the additional water before adding it when I transfer to the secondary.

Has anyone ever done anything like this before? Did it affect the taste at all?