gsDesign's sample size is rounded up to the nearest multiple of ratio + 1 when roundUpFinal = TRUE is specified. If roundUpFinal = FALSE, the final sample size is rounded to the nearest multiple of ratio + 1. (see https://github.com/keaven/gsDesign/blob/master/R/toInteger.R#L88-#L92)

In the current version of gsDesign2, the FA sample size is always round up to the nearest multiple of ratio +1. Besides, we will check if the ratio is integer or not, similar to gsDesign https://github.com/keaven/gsDesign/blob/master/R/toInteger.R#L52.

Additionally, the ratio argument will be added with a default value of 0, for consistency with gsDesign, see https://github.com/keaven/gsDesign/blob/master/R/toInteger.R#L85