ok, here is the deal, what your DHCP option requires as an input and how that can be written in options. after 6.8
here are some examples:
setting "'10.10.10.10'" as a value will yield the same output as 0x0a0a0a0a
setting "s'10.10.10.10'" as a value will yield the same output as 0x31322e31322e31322e3132
If an option requires a string value, and you entered IP address and it got converted as a string, you have to use later one. However in places where IP address was required it is easier to enter the value, as you would still get visible IP address as we are used to it.
edit:
so here is description of option 66 from RFC:
9.4 TFTP server name
This option is used to identify a TFTP server when the 'sname' field
in the DHCP header has been used for DHCP options.
The code for this option is 66, and its minimum length is 1.
Code Len TFTP server
+-----+-----+-----+-----+-----+---
| 66 | n | c1 | c2 | c3 | ...
+-----+-----+-----+-----+-----+---
as you can see you have to enter characters. And minimal length is 1, if that was IP address minimal length would be 4
like Option 50:
9.1. Requested IP Address
This option is used in a client request (DHCPDISCOVER) to allow the
client to request that a particular IP address be assigned.
The code for this option is 50, and its length is 4.
Code Len Address
+-----+-----+-----+-----+-----+-----+
| 50 | 4 | a1 | a2 | a3 | a4 |
+-----+-----+-----+-----+-----+-----+
where you have to specify IP address you want to request.
Also, if you are unsure about how exactly you have to enter what, you have to use the next-server option in DHCP-server network. Just see the manual, on what should be entered there (it will require an IP address in decimal)