Is the negative potential of 書く used in this sentence and what is its meaning?


I am reading a manga and a girl is showing her tutor that she "started her
test." All she has is her name written down. Here is the sentence.
お前しか書けてないがいいぞ. I believe the tutor has said this. The preceding sentence was
said by the girl and was 私もう始めてます。

I can't quite pick up on what is being said here. It seems like 書けてない is the
negative potential form of 書く. So my obviously wrong translation is, "Not
being able to only write your name is good." This makes no sense. I'm just
taking every word at face value so to speak. If anyone could provide a proper
meaning for this sentence, I would greatly appreciate it.




I think it's:

> **名** 前しか書けてないがいいぞ。

しか...ない means "no(thing)...but" → "only". (not "not...only")

書けてない is a contracted pronunciation of 書けていない. ～ていない can mean "have not done
(yet)". (See: [Why is a verb in the past (た形) contradicted with
～ていない?](https://japanese.stackexchange.com/q/42242/9831) ) ～しか書けていない here
literally means "have not been able to write anything but~~" "(have) managed
to write only~~".

The が means "but". (It's a conjunctive particle, not the subject case
particle.)

So the whole sentence means:

> "You've only written your name, but it's good."




I think it's:

> **名** 前しか書けてないがいいぞ。

しか...ない means "no(thing)...but" → "only". (not "not...only")

書けてない is a contracted pronunciation of 書けていない. ～ていない can mean "have not done
(yet)". (See: [Why is a verb in the past (た形) contradicted with
～ていない?](https://japanese.stackexchange.com/q/42242/9831) ) ～しか書けていない here
literally means "have not been able to write anything but~~" "(have) managed
to write only~~".

The が means "but". (It's a conjunctive particle, not the subject case
particle.)

So the whole sentence means:

> "You've only written your name, but it's good."

