Dual Ratio CTs

Not sure if this answers your question. Class 0.5 roughly means that the error is less than or equal to 0.5%.

The actual accuracy would be greater for the higher turns ratio (200 A range), according to this.

"Considering a core of certain fixed dimensions and magnetic materials with a secondary winding of say 200 turns (current ratio 200/1 turns ratio 1/200) and say it takes 2 amperes of the 200A primary current to magnetize the core, the error is therefore only 1% approximately. However considering a 50/1 CT with 50 secondary turns on the same core it still takes 2 amperes to magnetize to core. The error is then 4% approximately. To obtain a 1% accuracy on the 50/1 ring CT a much larger core and/or expensive core material is required"

https://electricalnotes.wordpress.com/2011/04/16/current-transformer/

My guess is that if it's rated Class 0.5/15VA, that that should apply to both ranges.

With multi-ratio CTs, it is the practice to underline one of the ratios. The declared CT parameters like VA and the accuracy apply to the ratio underlined.

In the subject case, if we assume the parameters are applicable to 200/1A ratio, at 100/1A ratio, the VA rating will be halved to 7.5VA to apply the same accuracy.