docs: improve grammar (#1726)

docs/modules/ngx_http_upstream_vnswrr_module.md

@@ -62,10 +62,10 @@ Enable `vnswrr` load balancing algorithm.
 - max_init
 
     The max number of virtual node per initialization, to avoid initializing too many virtual nodes in one request.
-    
+
     In very large clusters, setting this argument can significantly reduce the time overhead of a single request.
 
-    There is two another rules of `max_init`:
+    There are two additional rules of `max_init`:
     1. If `max_init` is not set or `0`, it will be adjusted to the number of peers.
     2. If `max_init` is greater than total weight of peers, it will be adjusted to the total weight of peers.
 
@@ -95,20 +95,20 @@ http {
 ## Performance
 
 
-In the same pressure environment (wrk, 500 concurrency, keepalive, 2000 endpoint), the CPU consumption of `VNSWRR` algorithm accounts for `0.27%` ( `ngx_http_upstream_get_vnswrr`).
+Under the same pressure (wrk, 500 concurrency, keepalive, 2000 endpoint), the CPU consumption of `VNSWRR` algorithm accounts for `0.27%` ( `ngx_http_upstream_get_vnswrr`).
 Compared with `VNSWRR` algorithm, the CPU consumption of `SWRR` (`ngx_http_upstream_get_peer` `39%`) is an order of magnitude higher than `VNSWRR`.
 
 
 ![image](/docs/image/vnswrr_vs_swrr_fhot.png)
 
-In the above environment, the QPS of `VNSWRR` increases by `60%` compared with `SWRR` algorithm.
+In the above environment, the QPS of `VNSWRR` increased by `60%` compared with `SWRR` algorithm.
 
 
 ![image](/docs/image/vnswrr_vs_swrr_2000.png)
 
 
 Observing the changes of QPS and RT in the different back-end number scenarios. 
-Under SWRR algorithm, when the number of back-end for every 500 addition, then the QPS of Nginx decreases by about 10% and RT increases by about 1 ms. But under the VNSWRR algorithm, QPS and RT do not change much.
+Under SWRR algorithm, with every 500 back-end servers added, the QPS of Nginx decreases by about 10% and RT increases by about 1 ms. But under the VNSWRR algorithm, QPS and RT do not change much.
 
 
 ![image](/docs/image/vnswrr_vs_swrr_qps.png)