DHCP Failover

It is VERY common for the last lease to be held by the primary. You are mixing up pool rebalancing and split value. 0 does not mean secondary has all the leases. It means that when things are work it should answer them all, but an "off by 1" is part of the deal. That is how pool rebalancing works. The last lease will *never* jump over to the other as you need to have at least two available leases to pool balance.

Only time any peer has full "ownership" of all leases is when you are in partner-down.

For more information on dhcp please find the man page dhcpd.conf.5.man

man dhcpd.conf