We made the same mistake you just made. Thought it was a 90 day Visa, did not notice the 60 day stamp at immigration and got a whopping 30 day overstayer fine. Next time we applied for a Tourist Visa we were given a hard time explaining why we were overstayers.
TLDR : Answer Summary
The user shares an experience regarding a misunderstanding about their visa duration, specifically mistaking a 60-day stamp for a 90-day visa. This led to a 30-day overstay fine and difficulties in future visa applications.