Sorry, the last part of your question...advanced maternal age (I hate that term) has nothing to do with HCG levels. In the majority of viable pregnancies of any age the HCG levels should increase quite quickly until they reach about 1200, then they gradually begin to slow down. Your Dr. should really repeat the test 2 to 3 days after the first one. Or, barring that, an ultrasound in about a week or so is a far more reliable means of determining viability. All the best to you.
Kitkat is correct. Normal HCG has a huge range and what the are looking for is the number to increase. At the level your at, in a perfect world, it would double in 48 to 72 hours. Was your Dr. concerned?
The number doesn't really matter, it's what that number does that determines a viable pregnancy. So if you see that number doubling over the next 2 days, then that's what you're looking for.