emulating AES GCM with AES CTR
In the NIST Special Publication 800-38D page #8 the maximum inputs lengths are defined in the standards as;


  The bit lengths of the input strings to the authenticated encryption function shall meet the
  following requirements: 



$len(P) \leq 2^{39}-256$


and in section 8.3 the number of invocations requirements for all implementations:


  The total number of invocations of the authenticated encryption function shall not exceed
  $2^{32}$, including all IV lengths and all instances of the authenticated encryption function with
  the given key. 



As a result, the recommendation doesn't advice the overflow of the counter.


We can find the maximum as:

$2^{32}$ invocation, per invocation you can encrypt 128-bit ($2^7$-bit) with AES, thus

$2^{32} \cdot 2^{7} = 2^{39}\text{-bit} \approx 68.7\text{GB}$ is the maximum data that one can encrypt with AES-GCM under the NIST recomendation.