What is the maximum jail time for misdemeanors?

Short part of the story, the State is trying to charge me with 21 counts of animal cruelty, all misdemeanors and all under the same case number. My PD is telling me I am facing up to 21 years jail time and that I should take the plea of 8 months. This is my first time ever being in any kind of trouble. Between friends and some family members that have dealt with the system they are all saying they can't stack the charges like that and it doesn't matter how many they add on the max jail time is still 1 year, not a year per charge. They also only have 15 counts in the incident report and have only sent discovery for those particular 15 counts. Wouldn't they need to drop charges they don't send evidence to back up?