Hi, I'm about to make only my second wine kit. The first time I didn't own a hydrometer, so I bought one this time. I'm looking to take a first reading, but wondered when to do so? I know it's pre-yeast, but the kit states I'm supposed to add the yeast and 3 litres of water, then top it up after the 3 days (primary) to 5 litres. Should I take the reading with the initial mixture of grape juice, water and sugar? Will topping up 3 days later not affect what the first reading should be? Thanks in advance.