Hello Pob19,
We know how important it is for your health data to reflect properly, and we're here to help. In additional to being able to add data, you are able to also delete the data you've added so you can update it with the correct details. To have the opportunity to delete the entry you would want go in to the Health app tap on Activity, followed by the data type in question. On the screen that appears scroll all the way down the page, then tap on Show All Data. You'll see a full list of the entries on this screen. You can either tap 'Edit' towards the top-right followed by the minus sign next to the data you want to remove to delete the entry, or you can swipe from right to left across the entry, then tap delete.
You can find more information in 'Manage Health data on your iPhone, iPod touch, or Apple Watch'.
Take care!