Too many factors to say for sure.
The absolute best way it to build it backwards.
Temporarily tape the leadcore to the reel’s spool.
Reel on the desired amount (say 7-10 colors)
Tie on your backer.
Fill the reel until 1/8″ from full with backer.
Now you have a couple options. Building two identical reels is the easiest. Zero the counter on the empty reel and reel in the backer. Write down the number. Then reel in your core and put on the leader.
On your now empty reel, zero the counter and reel in backer until your number matches. The add on the same amount of colors.
If you’re just building one reel, there’s two options.
If you have a big open area, you can pay all the line off and reel it back on from the opposite side.
Option two takes a drill and two empty fishing line spools. Wind the line off the reel onto a spool with the drill. Take the spool off and wind it onto yet another spool with the drill (now it’s flipped). Lastly reel it back onto the reel.
If you’re just using the reel for walleye fishing, I’d use mono for backer (cheaper, thicker, and you’ll never “need it”) It’s only purpose is to fill the spool to max capacity for optimum gear ratio and more accurate line counting.