Someone got it wrong - Help with record conflicts

Hello! Reading it sounds like some here might have experience that could help me? I've found some conflicting records and online family trees that may or may not be correct. I was looking into the family of Sigvald Johan Olson and Gunvor Gunvaldsdatter of Wisconsin, US. Their tombstones list birth/death dates of: * Sigvald 1819 - 1899 * Gunar 1830 - 1899 I can find Sigvald Johan Olson in Norway, b1819 and his wife Gunvor which appears to be an older version of Gunar. However when I look her up she wasn't born in 1830. In fact, according to baptism records Gunvor Gunvaldsdatter was born 26 nov 1824 and she had a brother Gunvor Gunvaldsen who was born 28 jun 1829. I found the two records on ancestry's website. Parents on both birth records were Gunvald Christensen and Ane Nielsdr (Nielsdatter). So I'm trying to figure out if I have the wrong Gunvor/Gunar or if I found the wrong records in Norway, or if someone put the wrong birth year on her headstone? I've seen wrong dates on headstones that happen before but it's not very common. Thanks everyone! I greatly appreciate any suggestions.