Invalid GMT offsets for minutes

[talesid5]

For round-off values, GMT is correct like for Pakistan its +5 so its ok, but for the areas with GMT offset with 30 minutes is invalid like in India GMT is acually +5:30 but its giving 5.
airports.find((airport) => airport.code === 'AMD') is giving:

{
  code: 'AMD',
  countryCode: 'IN',
  timezone: 'Asia/Kolkata',
  offset: { gmt: 5, dst: 5 }
}

whereas, it should be something like:
{..., offset: { gmt: '5:30', dst: '5:50' }} or {..., offset: { gmt: 5.5, dst: 5.5 }}