How should I understand the last sentence?
Rabbits generally eat pellets and plenty of green vegetables; they will also eat hay. They like to be held but shouldn’t be handled too much the first few days after purchasing, in order to adjust.
Two separate thoughts are expressed:
It is is dangerous to touch bare wires in an outlet, but it safe to do so if the mains circuit breaker is shut.
They like to be held but shouldn’t be handled too much.
Understandably, "held" and "handled" seem like the same thing, but there is a slight difference.
To hold something simply means to have in your hands, or cradled in your arms.
To handle something means to feel or manipulate with the hands.
I'm not a rabbit expert, but I would say that the instruction is you can certainly pick up the rabbit, perhaps cradle it. But perhaps limit the amount of stroking (or petting in American English).
Notice that the final part of the statement which you did not bold places a condition that the rule on "handling" only applies in "the first few days after purchasing". So perhaps the overall instruction is to limit (but not entirely restrict) all kinds of contact for that short period.