Kronos Holiday Confusion

Have 91 hours holiday balance on kronos and trying to book roughly 3 weeks holiday in june for a booked summer holiday,

Put in a request yesterday and was instantly refused (2 months notice)

Noticed i'd put (Full) Duration as opposed to (Hours)

I work 15 hour weeks and when im booking a week away on kronos i'm not sure what its calculating but theoretically I should have enough holiday correct?

91/15 should be roughly 6 weeks of holiday throughout the year, or am I mistaken?

I managed to get 2 weeks fairly easily last year and my manager edited the request to only give take 15 hours of balance per week as intended. How do I make this request in Kronos?

Unsure if this is clear enough.