fix truncation

src/view/com/util/numeric/format.ts

@@ -1,12 +1,26 @@
 import type {I18n} from '@lingui/core'
 
+import {isWeb} from '#/platform/detection'
+
+// `@formatjs/intl-numberformat/polyfill` doesn't support `roundingMode`, and
+// we'd ideally want `roundingMode: trunc` to properly display shortened counts
+// without it being rounded up, which can be misleading for follower count.
+const truncateRounding = (num: number): number => {
+  if (num < 1_000) {
+    return num
+  }
+
+  const factor = Math.floor((Math.log10(num) - 3) / 3) * 3 + 2
+  const pow = 10 ** factor
+
+  return Math.trunc(num / pow) * pow
+}
+
 export const formatCount = (i18n: I18n, num: number) => {
-  return i18n.number(num, {
+  return i18n.number(isWeb ? num : truncateRounding(num), {
     notation: 'compact',
     maximumFractionDigits: 1,
     // `1,953` shouldn't be rounded up to 2k, it should be truncated.
-    // @ts-expect-error: `roundingMode` doesn't seem to be in the typings yet
-    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat#roundingmode
     roundingMode: 'trunc',
   })
 }