The grooming fluid is a white fluid substance - which looks like milk. Guinea pigs produce this fluid when they groom themselves, a few drops can sometimes come out of their nose as well as their eyes, and the fluid drains away once the pig is finished grooming. It can take a fair few minutes to drain in some pigs, but it's usually gone within a minute in the majority. If it takes more than a few minutes to drain, or spills straight out of the eyes onto the hair around them (instead of draining away) it could indicate a blocked tear duct, although for some fluid to spill is pretty normal.
Some small "crusties" around the eyes are also normal, often just dried grooming fluid that has spilled over and accumulated. It would be more of a concern if the crusties around the eyes were very heavy and frequent, or coloured, or if there was active eye discharge (e.g. the eyes constantly running).