over sparge?

I did my first all grain brew session last Saturday. Very stoked. A friend gave me a little guidance the day before I brewed to basically just set my nerves at ease. Went great, no issues and the beer is happily fermenting away in my basement as I type.
My question is that he said in his first all grain brew that he over sparged and the end result was pretty bad because of it. It came up when I mentioned that my plan was to sparge until I had enough wort to do a 6.5 gallon boil. He said to be careful not to over do it because I would end up with a watered down product.
How would this be any different than topping off my carboy from a partial boil when brewing extract with partial mash?

Are you batch or fly sparging?

Fly sparging can be overdone, it affects the pH.

With either sparging style (and what I think your friend was getting at) you need to make sure that you do the proper calculations for mash volume, sparge volume, grain absorption, mash tun dead space, target volume pre and post boil etc. You can certainly "over sparge" and end up with a lower OG mash than expected.

Are you using a brewing software? If not I would try one of the free demos for beersmith, brewers friend, etc. These help with volumes a ton!

I'm certainly no expert, but as I understand it when you do a partial boil with extract, you are basically making a wort with a really high OG. You get the OG to where it should be by topping off the carboy with water at the end. In AG, you are extracting sugar from the grain, but as you sparge there is less sugar being extracted which is diluting your wort in terms of the OG.

I'm afraid this is an overly simplified answer, and probably full of errors, but that's how I understand it. I generally just follow the rule of 1-1.25 quarts of strike water per pound of grain, and 1/2 gallon of sparge water per pound of grain.

Don't worry about it. My first partial mash it happen to me washed the grains to many times. The beer still was good just didn't have the kick I was going for. Oh well you only do it once.

I am guessing I will be totally fine on this if the rule is 1.25 quarts per pound for strike and 1/2 gallon for sparge. I had roughly 13lbs of grain, 5ish gallons of strike and 3.5 gallons of sparge. Obviously lost some with absorption.
Do the programs like beersmith help with things like these day of brew calculations or just with the recipe generation piece? If it is worth he money, and helps with all that stuff too, makes sense to just get it.

Oh, and I did a fly sparge. Basically gently added my sparge water until I got the volume I needed.

Yes , we'll at least beersmith helps on brew day , strike and sparge volumes and temps( also adjusts for temp loss due to equipment and grain temps) plus has mash and boil timers . Damn I love beersmith